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+1
+00:00:00,000 --> 00:00:03,000
+(gentle piano music)
+
+2
+00:00:03,000 --> 00:00:04,000
+-: So in the previous video we have talked
+
+3
+00:00:04,000 --> 00:00:05,000
+about string, right?
+
+4
+00:00:05,000 --> 00:00:08,000
+Now we talk about this string,
+
+5
+00:00:08,000 --> 00:00:10,000
+what might be happening behind the scene.
+
+6
+00:00:10,000 --> 00:00:11,000
+Example, let's say if you store this navin,
+
+7
+00:00:11,000 --> 00:00:15,000
+of course it'll be getting stored in the heap memory.
+
+8
+00:00:15,000 --> 00:00:16,000
+But now what I wanna do is
+
+9
+00:00:16,000 --> 00:00:17,000
+before printing navin here,
+
+10
+00:00:17,000 --> 00:00:19,000
+let's say I want to append something.
+
+11
+00:00:19,000 --> 00:00:22,000
+So I would say name is equal to,
+
+12
+00:00:22,000 --> 00:00:25,000
+I want to add my name with, let's say reddy here.
+
+13
+00:00:25,000 --> 00:00:26,000
+I'm giving a space
+
+14
+00:00:26,000 --> 00:00:28,000
+so that we can differentiate these two words.
+
+15
+00:00:28,000 --> 00:00:30,000
+So of course now when I say name,
+
+16
+00:00:30,000 --> 00:00:32,000
+it'll be Navin Reddy, right?
+
+17
+00:00:32,000 --> 00:00:34,000
+So basically we are trying to change the value.
+
+18
+00:00:34,000 --> 00:00:36,000
+Now if we talk about integer, float, double.
+
+19
+00:00:36,000 --> 00:00:38,000
+Basically you can change values of it, right?
+
+20
+00:00:38,000 --> 00:00:39,000
+And it actually makes sense.
+
+21
+00:00:39,000 --> 00:00:42,000
+That's why we call them as variables.
+
+22
+00:00:42,000 --> 00:00:43,000
+And here also, we are trying to do that.
+
+23
+00:00:43,000 --> 00:00:46,000
+But first of all, let's check if this works.
+
+24
+00:00:46,000 --> 00:00:50,000
+So if I go back and compile and run, it works.
+
+25
+00:00:50,000 --> 00:00:51,000
+You can see that the new data
+
+26
+00:00:51,000 --> 00:00:52,000
+for the navin is navin reddy, right?
+
+27
+00:00:52,000 --> 00:00:54,000
+And that works.
+
+28
+00:00:54,000 --> 00:00:56,000
+But what if I say that's not the case?
+
+29
+00:00:56,000 --> 00:00:59,000
+You're not changing the existing string.
+
+30
+00:00:59,000 --> 00:01:00,000
+Let me repeat.
+
+31
+00:01:00,000 --> 00:01:04,000
+You are not changing from navin to navin reddy?
+
+32
+00:01:04,000 --> 00:01:07,000
+So if you're thinking there will be a variable here
+
+33
+00:01:07,000 --> 00:01:10,000
+where you have Navin, you're making it Navin Reddy.
+
+34
+00:01:10,000 --> 00:01:12,000
+No, that's not the case.
+
+35
+00:01:12,000 --> 00:01:14,000
+That's not how string works.
+
+36
+00:01:14,000 --> 00:01:15,000
+Okay, so what happens?
+
+37
+00:01:15,000 --> 00:01:18,000
+So what I will do is I'll just remove this part now.
+
+38
+00:01:18,000 --> 00:01:20,000
+So what is happening, basically,
+
+39
+00:01:20,000 --> 00:01:23,000
+you know, since strings are used heavily in Java,
+
+40
+00:01:23,000 --> 00:01:26,000
+now most of the time you try to reuse the strings,
+
+41
+00:01:26,000 --> 00:01:28,000
+the same string, you'll be using multiple times.
+
+42
+00:01:28,000 --> 00:01:31,000
+Example, let's say, before I show you something,
+
+43
+00:01:31,000 --> 00:01:33,000
+let's say, I create a string here,
+
+44
+00:01:33,000 --> 00:01:37,000
+which is s1 is equal to Navin.
+
+45
+00:01:37,000 --> 00:01:38,000
+And you can see we have a capital N this time.
+
+46
+00:01:38,000 --> 00:01:41,000
+So this two data are actually different, okay?
+
+47
+00:01:41,000 --> 00:01:44,000
+So I will say string s2 is equal to,
+
+48
+00:01:44,000 --> 00:01:45,000
+and I will say Navin again.
+
+49
+00:01:45,000 --> 00:01:47,000
+Now, what do you think?
+
+50
+00:01:47,000 --> 00:01:50,000
+How many objects we are creating behind the scene?
+
+51
+00:01:50,000 --> 00:01:51,000
+Think about this.
+
+52
+00:01:51,000 --> 00:01:51,000
+Okay?
+
+53
+00:01:51,000 --> 00:01:53,000
+So if you're thinking, we got two objects,
+
+54
+00:01:53,000 --> 00:01:57,000
+actually not, we got two references.
+
+55
+00:01:57,000 --> 00:01:58,000
+We got s1, s2.
+
+56
+00:01:58,000 --> 00:02:02,000
+Of course, in your stack, you'll be having s1, s2 here,
+
+57
+00:02:02,000 --> 00:02:06,000
+but in total, you got only one object.
+
+58
+00:02:08,000 --> 00:02:09,000
+And that sounds tricky here, right?
+
+59
+00:02:09,000 --> 00:02:11,000
+And let me prove that point to you.
+
+60
+00:02:11,000 --> 00:02:13,000
+See, what I want to prove is the value
+
+61
+00:02:13,000 --> 00:02:15,000
+for this field and this field will be equal.
+
+62
+00:02:15,000 --> 00:02:17,000
+The way the I can do that is by saying S out,
+
+63
+00:02:17,000 --> 00:02:22,000
+s1 is equal to equal to s2.
+
+64
+00:02:22,000 --> 00:02:25,000
+If this is true, then they are same.
+
+65
+00:02:25,000 --> 00:02:27,000
+So if I run, you can see we got true.
+
+66
+00:02:27,000 --> 00:02:31,000
+That means the value for the addresses are same.
+
+67
+00:02:31,000 --> 00:02:33,000
+In total we got only one object.
+
+68
+00:02:33,000 --> 00:02:37,000
+So here what happens is we have a special area
+
+69
+00:02:37,000 --> 00:02:39,000
+inside your heap memory.
+
+70
+00:02:39,000 --> 00:02:42,000
+So this is your heap, that's your JVM,
+
+71
+00:02:42,000 --> 00:02:44,000
+and that's your stack.
+
+72
+00:02:44,000 --> 00:02:45,000
+So inside your heap,
+
+73
+00:02:45,000 --> 00:02:50,000
+you'll be having a special area called string constant pool.
+
+74
+00:02:51,000 --> 00:02:54,000
+And by the name itself you can see it says constant.
+
+75
+00:02:54,000 --> 00:02:55,000
+That's right.
+
+76
+00:02:55,000 --> 00:02:58,000
+Every string which you create, which you use in Java,
+
+77
+00:02:58,000 --> 00:03:01,000
+which is a string literal is actually a constant.
+
+78
+00:03:01,000 --> 00:03:01,000
+You can't change it.
+
+79
+00:03:01,000 --> 00:03:04,000
+Example, if I write something like navin here,
+
+80
+00:03:04,000 --> 00:03:05,000
+I cannot change it.
+
+81
+00:03:05,000 --> 00:03:06,000
+It's done.
+
+82
+00:03:06,000 --> 00:03:08,000
+It's navin everywhere, okay?
+
+83
+00:03:08,000 --> 00:03:10,000
+So you can't change the data.
+
+84
+00:03:10,000 --> 00:03:12,000
+So example, what happens is every time you try
+
+85
+00:03:12,000 --> 00:03:14,000
+to use a variable here, example,
+
+86
+00:03:14,000 --> 00:03:16,000
+if you execute the line number eight, it checks,
+
+87
+00:03:16,000 --> 00:03:18,000
+okay, we need navin variable.
+
+88
+00:03:18,000 --> 00:03:21,000
+Do we already have navin in the string constant pool?
+
+89
+00:03:21,000 --> 00:03:22,000
+No, we don't have it.
+
+90
+00:03:22,000 --> 00:03:23,000
+So let's create navin here.
+
+91
+00:03:23,000 --> 00:03:25,000
+So it'll create a string variable, navin,
+
+92
+00:03:25,000 --> 00:03:27,000
+it'll have some address, let's say 101,
+
+93
+00:03:27,000 --> 00:03:31,000
+and then the name variable here will get this address.
+
+94
+00:03:31,000 --> 00:03:33,000
+So this name variable is actually referring
+
+95
+00:03:33,000 --> 00:03:36,000
+to this particular address, okay?
+
+96
+00:03:36,000 --> 00:03:38,000
+Then it goes for the next statement.
+
+97
+00:03:38,000 --> 00:03:39,000
+Let's execute this part.
+
+98
+00:03:39,000 --> 00:03:41,000
+Let's ignore this line as of now,
+
+99
+00:03:41,000 --> 00:03:42,000
+let's focus on line number 12 and 13.
+
+100
+00:03:42,000 --> 00:03:45,000
+So line number 12 says, s1 is equal to Navin.
+
+101
+00:03:45,000 --> 00:03:46,000
+Okay, so it checks,
+
+102
+00:03:46,000 --> 00:03:49,000
+do we have navin with capital N in the string pool?
+
+103
+00:03:49,000 --> 00:03:50,000
+No, we don't have it.
+
+104
+00:03:50,000 --> 00:03:52,000
+So it'll create Navin here.
+
+105
+00:03:52,000 --> 00:03:54,000
+And let's say the address is 103.
+
+106
+00:03:54,000 --> 00:03:57,000
+So it'll store 103 here.
+
+107
+00:03:57,000 --> 00:03:58,000
+Now that makes sense, right?
+
+108
+00:03:58,000 --> 00:04:00,000
+And that's why you're referring to that particular location.
+
+109
+00:04:00,000 --> 00:04:02,000
+Now, what happens on line number 13?
+
+110
+00:04:02,000 --> 00:04:05,000
+Line number 13 says string s2 is equal to Navin.
+
+111
+00:04:05,000 --> 00:04:07,000
+It'll go to string constant pool again
+
+112
+00:04:07,000 --> 00:04:09,000
+and check, hey, do we have Navin with capital N?
+
+113
+00:04:09,000 --> 00:04:10,000
+Yes, we do have.
+
+114
+00:04:10,000 --> 00:04:13,000
+Now, it'll not create a new object for you,
+
+115
+00:04:13,000 --> 00:04:16,000
+it'll simply use this address 103.
+
+116
+00:04:16,000 --> 00:04:17,000
+Okay?
+
+117
+00:04:17,000 --> 00:04:18,000
+And that's the beauty.
+
+118
+00:04:18,000 --> 00:04:20,000
+That's how you're trying to save the memory.
+
+119
+00:04:20,000 --> 00:04:23,000
+Otherwise you could have created multiple variables
+
+120
+00:04:23,000 --> 00:04:24,000
+with the same data.
+
+121
+00:04:24,000 --> 00:04:25,000
+So it doesn't make sense, right?
+
+122
+00:04:25,000 --> 00:04:27,000
+And that's why it uses a string constant pool.
+
+123
+00:04:27,000 --> 00:04:30,000
+Now, my question to you is, what is happening here?
+
+124
+00:04:30,000 --> 00:04:33,000
+Now when I say you can't change the data,
+
+125
+00:04:33,000 --> 00:04:36,000
+that means you cannot simply update this particular
+
+126
+00:04:36,000 --> 00:04:37,000
+navin by Navin Reddy?
+
+127
+00:04:37,000 --> 00:04:40,000
+No, that's not happening, navin is still there.
+
+128
+00:04:40,000 --> 00:04:42,000
+It's a constant. You can't change this.
+
+129
+00:04:42,000 --> 00:04:43,000
+Now on line number 9,
+
+130
+00:04:43,000 --> 00:04:47,000
+what is happening is it is creating a new object
+
+131
+00:04:47,000 --> 00:04:51,000
+which will have a data which is navin reddy,
+
+132
+00:04:51,000 --> 00:04:53,000
+let's say it has the address, which is 105.
+
+133
+00:04:53,000 --> 00:04:54,000
+So on line number 9,
+
+134
+00:04:54,000 --> 00:04:58,000
+basically what you're doing is you are changing this address
+
+135
+00:04:58,000 --> 00:05:01,000
+from 101 to 105.
+
+136
+00:05:01,000 --> 00:05:04,000
+You are just changing the address.
+
+137
+00:05:04,000 --> 00:05:06,000
+You're not changing the actual data.
+
+138
+00:05:06,000 --> 00:05:09,000
+You are basically creating a new object.
+
+139
+00:05:09,000 --> 00:05:09,000
+Okay?
+
+140
+00:05:09,000 --> 00:05:12,000
+Now, you might be thinking what will happen to navin here?
+
+141
+00:05:12,000 --> 00:05:13,000
+The thing is,
+
+142
+00:05:13,000 --> 00:05:16,000
+now this particular object is eligible
+
+143
+00:05:16,000 --> 00:05:17,000
+for garbage collection.
+
+144
+00:05:17,000 --> 00:05:19,000
+It'll be removed after some time,
+
+145
+00:05:19,000 --> 00:05:21,000
+just to get some memory back.
+
+146
+00:05:21,000 --> 00:05:22,000
+Okay?
+
+147
+00:05:22,000 --> 00:05:24,000
+So point to remember is once you create this object,
+
+148
+00:05:24,000 --> 00:05:25,000
+you can't change it.
+
+149
+00:05:25,000 --> 00:05:28,000
+And that's where we have some terms to remember.
+
+150
+00:05:28,000 --> 00:05:29,000
+And the terms are,
+
+151
+00:05:29,000 --> 00:05:33,000
+so there's a concept of mutable strings
+
+152
+00:05:33,000 --> 00:05:35,000
+and immutable string.
+
+153
+00:05:35,000 --> 00:05:36,000
+Now, what is mutable means?
+
+154
+00:05:36,000 --> 00:05:40,000
+Mutable means change something which can be changed.
+
+155
+00:05:40,000 --> 00:05:43,000
+And immutable means unchanged or you cannot change it.
+
+156
+00:05:43,000 --> 00:05:46,000
+So basically, by default strings are immutable.
+
+157
+00:05:46,000 --> 00:05:48,000
+Once you create the object, you can't change it.
+
+158
+00:05:48,000 --> 00:05:49,000
+And that's very important remember,
+
+159
+00:05:49,000 --> 00:05:51,000
+it's immutable string, okay?
+
+160
+00:05:51,000 --> 00:05:53,000
+So whatever data you're creating here is immutable.
+
+161
+00:05:53,000 --> 00:05:55,000
+But what if you want mutable string?
+
+162
+00:05:55,000 --> 00:05:58,000
+And that's why we have two different classes in Java to use.
+
+163
+00:05:58,000 --> 00:06:00,000
+Instead of using string,
+
+164
+00:06:00,000 --> 00:06:04,000
+you can use something called a string buffer
+
+165
+00:06:04,000 --> 00:06:07,000
+or a string builder.
+
+166
+00:06:07,000 --> 00:06:09,000
+Now, both are very similar with one difference
+
+167
+00:06:09,000 --> 00:06:10,000
+that defense we'll discuss later,
+
+168
+00:06:10,000 --> 00:06:14,000
+but they both are similar and they both provide you a way
+
+169
+00:06:14,000 --> 00:06:18,000
+to implement a immutable string.
+
+170
+00:06:18,000 --> 00:06:18,000
+Okay?
+
+171
+00:06:18,000 --> 00:06:19,000
+Now, how do we do that?
+
+172
+00:06:19,000 --> 00:06:22,000
+That we'll see in the upcoming videos.
+
diff --git a/02 - Core Java/039 Source-code.url b/02 - Core Java/039 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/039 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/040 Source-code.url b/02 - Core Java/040 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/040 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/040 StringBuffer and StringBuilder_en.srt b/02 - Core Java/040 StringBuffer and StringBuilder_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..1619b150d420becfe1f32c865659dc5526c7d438
--- /dev/null
+++ b/02 - Core Java/040 StringBuffer and StringBuilder_en.srt	
@@ -0,0 +1,620 @@
+1
+00:00:00,000 --> 00:00:03,000
+(soft chimes)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: In this video, we'll work with string buffer.
+
+3
+00:00:05,000 --> 00:00:07,000
+So, what we have is we have a string anvil
+
+4
+00:00:07,000 --> 00:00:09,000
+and we have work with it, right?
+
+5
+00:00:09,000 --> 00:00:11,000
+So I'll do is remove everything
+
+6
+00:00:11,000 --> 00:00:13,000
+and let's work with string buffer.
+
+7
+00:00:13,000 --> 00:00:15,000
+So I'll say string buffer
+
+8
+00:00:15,000 --> 00:00:16,000
+and lets create a reference call it
+
+9
+00:00:16,000 --> 00:00:19,000
+equal to new... string buffer
+
+10
+00:00:19,000 --> 00:00:21,000
+so when we talk about string buffer
+
+11
+00:00:21,000 --> 00:00:22,000
+of course in this string buffer, you will have a string
+
+12
+00:00:22,000 --> 00:00:25,000
+and if which is actually mutable
+
+13
+00:00:25,000 --> 00:00:26,000
+you can change it...
+
+14
+00:00:26,000 --> 00:00:27,000
+now to make it more efficient
+
+15
+00:00:27,000 --> 00:00:28,000
+you know what string buffer does?
+
+16
+00:00:28,000 --> 00:00:31,000
+String buffer will give you a "buffer size".. okay?
+
+17
+00:00:31,000 --> 00:00:33,000
+Which is of 16 bytes
+
+18
+00:00:33,000 --> 00:00:34,000
+so I can. I can just try to print that first
+
+19
+00:00:34,000 --> 00:00:36,000
+I will say sb. 'dot'
+
+20
+00:00:36,000 --> 00:00:39,000
+so we can know the capacity of the string buffer
+
+21
+00:00:39,000 --> 00:00:41,000
+even if its empty, it will give a capacity
+
+22
+00:00:41,000 --> 00:00:43,000
+of 16 characters and you got it there .
+
+23
+00:00:43,000 --> 00:00:46,000
+In fact, you can also provide some initial string here,..
+
+24
+00:00:46,000 --> 00:00:48,000
+So let's say.. uhh... if I say
+
+25
+00:00:48,000 --> 00:00:48,000
+"Navin" here
+
+26
+00:00:48,000 --> 00:00:51,000
+now Navin is a 5 charters right? This is how
+
+27
+00:00:51,000 --> 00:00:53,000
+you basically create a string buffer.. in bracket
+
+28
+00:00:53,000 --> 00:00:54,000
+you will mention the string
+
+29
+00:00:54,000 --> 00:00:56,000
+so, it will create a string buffer object
+
+30
+00:00:56,000 --> 00:00:59,000
+and the beauty is you can change this data.
+
+31
+00:00:59,000 --> 00:01:02,000
+Okay.. now the thing is..uhh.. if you talk about
+
+32
+00:01:02,000 --> 00:01:03,000
+capacity what it will be?..
+
+33
+00:01:03,000 --> 00:01:06,000
+So capacity is..it should be still 16 right?
+
+34
+00:01:06,000 --> 00:01:07,000
+No. It actually changes
+
+35
+00:01:07,000 --> 00:01:10,000
+if you can see.. the capacity will become 21.
+
+36
+00:01:10,000 --> 00:01:12,000
+It's because.. it will store my name and it
+
+37
+00:01:12,000 --> 00:01:16,000
+will also give me a 16 space extra.
+
+38
+00:01:16,000 --> 00:01:18,000
+Now why it gives me that space is because..
+
+39
+00:01:18,000 --> 00:01:21,000
+Every time we'll change data, and if it consumes
+
+40
+00:01:21,000 --> 00:01:24,000
+a continuous memory location inside your heap memory
+
+41
+00:01:24,000 --> 00:01:26,000
+and what if there's no continuous location next
+
+42
+00:01:26,000 --> 00:01:28,000
+(fumbles).. I mean Th.. what if there is no location
+
+43
+00:01:28,000 --> 00:01:30,000
+available. There's no space available.
+
+44
+00:01:30,000 --> 00:01:32,000
+In that case, it has to relocate. So to
+
+45
+00:01:32,000 --> 00:01:34,000
+reduce the relo.. relocation of the string
+
+46
+00:01:34,000 --> 00:01:37,000
+it gives you a buffer. Okay.
+
+47
+00:01:37,000 --> 00:01:40,000
+So that's the capacity and now we know how it works.
+
+48
+00:01:40,000 --> 00:01:42,000
+We can also print the length of the string and we can
+
+49
+00:01:42,000 --> 00:01:45,000
+say... sb.length. And length is available in
+
+50
+00:01:45,000 --> 00:01:48,000
+normal string as well. So if I compile
+
+51
+00:01:48,000 --> 00:01:50,000
+and run, you can see the length is 5
+
+52
+00:01:50,000 --> 00:01:52,000
+so, length and capacities are 2 different things.
+
+53
+00:01:52,000 --> 00:01:56,000
+Okay, now can I append data?
+
+54
+00:01:56,000 --> 00:01:58,000
+See, the ultimate thing was.. can I change
+
+55
+00:01:58,000 --> 00:02:00,000
+my data, which is "Navin" in this case.
+
+56
+00:02:00,000 --> 00:02:03,000
+The beauty is string buffer will give you
+
+57
+00:02:03,000 --> 00:02:05,000
+a lot of different methods to do that..
+
+58
+00:02:05,000 --> 00:02:06,000
+You can see we have a metho...method called
+
+59
+00:02:06,000 --> 00:02:08,000
+append.. so you can use append
+
+60
+00:02:08,000 --> 00:02:10,000
+and you can append a data which you want to..
+
+61
+00:02:10,000 --> 00:02:13,000
+So lets say I want to append.. "Reddy" here,
+
+62
+00:02:13,000 --> 00:02:14,000
+and of course I want to give a space
+
+63
+00:02:14,000 --> 00:02:17,000
+between "Navin" uhh.. "Navin" and "Reddy".
+
+64
+00:02:17,000 --> 00:02:19,000
+So you can append and you can print the data...
+
+65
+00:02:19,000 --> 00:02:21,000
+So you can print 'sb' as it is..
+
+66
+00:02:21,000 --> 00:02:23,000
+Let's.. uh. First we have to compile the
+
+67
+00:02:23,000 --> 00:02:25,000
+code.. Run. And you can see the code
+
+68
+00:02:25,000 --> 00:02:27,000
+"Navin" "Reddy" it wo.. that works.
+
+69
+00:02:27,000 --> 00:02:30,000
+Next, what if you want to assign string buffer
+
+70
+00:02:30,000 --> 00:02:32,000
+data to string is example if I do that..uh,
+
+71
+00:02:32,000 --> 00:02:35,000
+you can see.. it will... give you a log.
+
+72
+00:02:35,000 --> 00:02:37,000
+It says, type mismatch: cannot convert from
+
+73
+00:02:37,000 --> 00:02:39,000
+string buffer to String.. oo of course
+
+74
+00:02:39,000 --> 00:02:42,000
+right? HTI is of type string, so in that case
+
+75
+00:02:42,000 --> 00:02:45,000
+you can get the string back.. do we have
+
+76
+00:02:45,000 --> 00:02:46,000
+a method for it?
+
+77
+00:02:46,000 --> 00:02:48,000
+Lets see...yes we do have two string
+
+78
+00:02:48,000 --> 00:02:49,000
+we can use that
+
+79
+00:02:49,000 --> 00:02:52,000
+I think that's the only method we can use...
+
+80
+00:02:52,000 --> 00:02:53,000
+Yup, so let's see those two string.
+
+81
+00:02:53,000 --> 00:02:56,000
+So, basically you can use two string to convert
+
+82
+00:02:56,000 --> 00:02:58,000
+the.. . string buffer data. I mean it will
+
+83
+00:02:58,000 --> 00:03:01,000
+get the string format, it was stored in HTR
+
+84
+00:03:01,000 --> 00:03:03,000
+and you can print it.
+
+85
+00:03:03,000 --> 00:03:05,000
+Okay. We can use that... what else we can do
+
+86
+00:03:05,000 --> 00:03:06,000
+with string buffer?
+
+87
+00:03:06,000 --> 00:03:09,000
+If I come back here if I say sb'dot',
+
+88
+00:03:09,000 --> 00:03:11,000
+you can see we have so many methods here.
+
+89
+00:03:11,000 --> 00:03:13,000
+Okay, so we have append.. we have chars, it will give you
+
+90
+00:03:13,000 --> 00:03:17,000
+a character... we have done that
+
+91
+00:03:17,000 --> 00:03:19,000
+okay, so we can also delete something, we can
+
+92
+00:03:19,000 --> 00:03:20,000
+delete a character at an index. So next
+
+93
+00:03:20,000 --> 00:03:23,000
+I will delete a character at location "2".
+
+94
+00:03:23,000 --> 00:03:27,000
+If you try to delete that data..compile and.. run.
+
+95
+00:03:27,000 --> 00:03:29,000
+You can see we got, oh! Something is missing
+
+96
+00:03:29,000 --> 00:03:30,000
+the way is missing there.
+
+97
+00:03:30,000 --> 00:03:33,000
+Because that is at index number "2"
+
+98
+00:03:33,000 --> 00:03:35,000
+okay, so the idea is we basically we can change it
+
+99
+00:03:35,000 --> 00:03:37,000
+and you can experiment it a lot.
+
+100
+00:03:37,000 --> 00:03:41,000
+You can try to use different methods, we can delete,
+
+101
+00:03:41,000 --> 00:03:43,000
+we can insert also in between, lets say
+
+102
+00:03:43,000 --> 00:03:46,000
+I want to insert .. uh. Java at the start,
+
+103
+00:03:46,000 --> 00:03:48,000
+you can do that. So you can say insert
+
+104
+00:03:48,000 --> 00:03:49,000
+you can mention the index value where you want
+
+105
+00:03:49,000 --> 00:03:52,000
+to insert exact location, and the data that you
+
+106
+00:03:52,000 --> 00:03:54,000
+..which you want to insert. So I will say
+
+107
+00:03:54,000 --> 00:03:56,000
+Java 'space', now what it will do is
+
+108
+00:03:56,000 --> 00:04:00,000
+It will add Java at index 0, I mean that is start
+
+109
+00:04:00,000 --> 00:04:02,000
+itself. So if I run, you can see it says Java..
+
+110
+00:04:02,000 --> 00:04:05,000
+Of course you can add Java in between as well.
+
+111
+00:04:05,000 --> 00:04:08,000
+Uh.. lets say I want to add.. after...
+
+112
+00:04:08,000 --> 00:04:10,000
+5th location I think... that should work.
+
+113
+00:04:10,000 --> 00:04:13,000
+After this space it's 6, so let's try that..
+
+114
+00:04:13,000 --> 00:04:15,000
+Compile Run. You can see its.. "Navin"
+
+115
+00:04:15,000 --> 00:04:17,000
+"Java", "Reddy" so it works.
+
+116
+00:04:17,000 --> 00:04:20,000
+Okay.. so, yeah that's how we can basically use insert
+
+117
+00:04:20,000 --> 00:04:22,000
+we have more methods to explore and I would
+
+118
+00:04:22,000 --> 00:04:24,000
+recommend you to do that. Can we just see
+
+119
+00:04:24,000 --> 00:04:26,000
+one more.. We can also get the substring..
+
+120
+00:04:26,000 --> 00:04:27,000
+Let's say if you have a very big string
+
+121
+00:04:27,000 --> 00:04:30,000
+you can specify.. the starting point, ending point
+
+122
+00:04:30,000 --> 00:04:33,000
+using substring. You can set the length as well.
+
+123
+00:04:33,000 --> 00:04:36,000
+So If you set the length of the stream, let's
+
+124
+00:04:36,000 --> 00:04:38,000
+say I want to set the length of "30".
+
+125
+00:04:38,000 --> 00:04:40,000
+So, if you want to add your data and
+
+126
+00:04:40,000 --> 00:04:42,000
+if you want to have a specific length..
+
+127
+00:04:42,000 --> 00:04:43,000
+Which is 30 here.
+
+128
+00:04:43,000 --> 00:04:44,000
+It will save the data which is whatever
+
+129
+00:04:44,000 --> 00:04:46,000
+you have. "Navin" 20 will be stored and
+
+130
+00:04:46,000 --> 00:04:47,000
+all the other values will be... will be
+
+131
+00:04:47,000 --> 00:04:49,000
+null.. let's see. So after "Navin" Reddy" it will
+
+132
+00:04:49,000 --> 00:04:52,000
+add some extra data here... okay.
+
+133
+00:04:52,000 --> 00:04:54,000
+So that you can replace that later. Cool.. we
+
+134
+00:04:54,000 --> 00:04:57,000
+can do that... we can also set a minimum or
+
+135
+00:04:57,000 --> 00:04:59,000
+maximum data. I think there's minimum capacity
+
+136
+00:04:59,000 --> 00:05:02,000
+method which we can use... I think the method
+
+137
+00:05:02,000 --> 00:05:05,000
+name is "ensurecapacity", yeah okay.
+
+138
+00:05:05,000 --> 00:05:08,000
+So we can, we can set the ensurecapacity to 100
+
+139
+00:05:08,000 --> 00:05:11,000
+so it..minimum, minimum capacity will be 100.
+
+140
+00:05:11,000 --> 00:05:13,000
+Okay um that's how you have different methods.
+
+141
+00:05:13,000 --> 00:05:15,000
+Now what's the difference between string buffer and
+
+142
+00:05:15,000 --> 00:05:17,000
+string builder. So as I mentioned we also have
+
+143
+00:05:17,000 --> 00:05:18,000
+string builder right?..there's only one
+
+144
+00:05:18,000 --> 00:05:22,000
+difference, string buffer is thread safe and
+
+145
+00:05:22,000 --> 00:05:23,000
+string builder is not..
+
+146
+00:05:23,000 --> 00:05:25,000
+Now what is thread safe means that we
+
+147
+00:05:25,000 --> 00:05:26,000
+will understand once we talk about
+
+148
+00:05:26,000 --> 00:05:29,000
+thread concept.. so that point also ..
+
+149
+00:05:29,000 --> 00:05:31,000
+we'll talk about difference between string buffer
+
+150
+00:05:31,000 --> 00:05:33,000
+and string builder, but what other methods
+
+151
+00:05:33,000 --> 00:05:35,000
+you have in string buffer is almost
+
+152
+00:05:35,000 --> 00:05:37,000
+the same as string builder. So if you
+
+153
+00:05:37,000 --> 00:05:39,000
+know one.. you know the other one as well.
+
+154
+00:05:39,000 --> 00:05:41,000
+Okay, so that's about string buffer and...
+
+155
+00:05:41,000 --> 00:05:43,000
+Some of the methods of string.
+
diff --git a/02 - Core Java/041 Source-code.url b/02 - Core Java/041 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/041 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/041 Static Variable_en.srt b/02 - Core Java/041 Static Variable_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..bb8aa875755fd0b956614af528b1ac5214af9d74
--- /dev/null
+++ b/02 - Core Java/041 Static Variable_en.srt	
@@ -0,0 +1,700 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, we'll talk about static keyword.
+
+3
+00:00:06,000 --> 00:00:08,000
+From the start itself, when we have written the first code,
+
+4
+00:00:08,000 --> 00:00:10,000
+we are looking at the static keyword,
+
+5
+00:00:10,000 --> 00:00:12,000
+and the question still remains, right,
+
+6
+00:00:12,000 --> 00:00:14,000
+what is the static?
+
+7
+00:00:14,000 --> 00:00:15,000
+So we know what is method is,
+
+8
+00:00:15,000 --> 00:00:17,000
+we know what is return type, we know what is class.
+
+9
+00:00:17,000 --> 00:00:21,000
+But again, problem gets stuck here in static itself.
+
+10
+00:00:21,000 --> 00:00:23,000
+Now to make you understand this, let's take an example here.
+
+11
+00:00:23,000 --> 00:00:26,000
+So let's say we have an example of mobile phone,
+
+12
+00:00:26,000 --> 00:00:28,000
+and every mobile phone has a brand.
+
+13
+00:00:28,000 --> 00:00:31,000
+So brand will be string, so it's String brand,
+
+14
+00:00:32,000 --> 00:00:34,000
+and we can have a default value for it.
+
+15
+00:00:34,000 --> 00:00:37,000
+We can have int, which is price,
+
+16
+00:00:37,000 --> 00:00:42,000
+and then String network, okay?
+
+17
+00:00:43,000 --> 00:00:46,000
+And we can also make it for a specific brand as well,
+
+18
+00:00:46,000 --> 00:00:47,000
+but let's keep it simple.
+
+19
+00:00:47,000 --> 00:00:49,000
+Let's have a mobile phone, different brands,
+
+20
+00:00:49,000 --> 00:00:53,000
+different price, different network, and we'll say name.
+
+21
+00:00:53,000 --> 00:00:56,000
+Okay, now see name itself of a mobile phone changes, right?
+
+22
+00:00:56,000 --> 00:01:00,000
+So we used to say normal phones, then we got smartphones,
+
+23
+00:01:00,000 --> 00:01:02,000
+and now we have foldable phones, right?
+
+24
+00:01:02,000 --> 00:01:04,000
+So we can have a different name to phones nowadays.
+
+25
+00:01:04,000 --> 00:01:06,000
+Every phone is called a smartphone now
+
+26
+00:01:06,000 --> 00:01:08,000
+because that's what we call it.
+
+27
+00:01:08,000 --> 00:01:09,000
+Usually, we used to call it mobile,
+
+28
+00:01:09,000 --> 00:01:11,000
+then we used to call it phone, right?
+
+29
+00:01:11,000 --> 00:01:13,000
+So we have a name here as well.
+
+30
+00:01:13,000 --> 00:01:16,000
+What do you call a mobile phone? So now it's a smartphone.
+
+31
+00:01:16,000 --> 00:01:18,000
+Okay, so if you want to work with this mobile phone,
+
+32
+00:01:18,000 --> 00:01:19,000
+of course, you have to create an object, right?
+
+33
+00:01:19,000 --> 00:01:21,000
+So if I say Mobile obj,
+
+34
+00:01:21,000 --> 00:01:24,000
+if I will say Mobile obj1 = new Mobile.
+
+35
+00:01:24,000 --> 00:01:26,000
+And of course, every mobile will have
+
+36
+00:01:26,000 --> 00:01:27,000
+a different parameter here.
+
+37
+00:01:27,000 --> 00:01:29,000
+What I will do is I will just remove this network just
+
+38
+00:01:29,000 --> 00:01:32,000
+to keep it simple, we just want three variables here,
+
+39
+00:01:32,000 --> 00:01:35,000
+obj1.brand, I want to set the brand here.
+
+40
+00:01:35,000 --> 00:01:37,000
+Let's say the brand is Apple
+
+41
+00:01:37,000 --> 00:01:39,000
+since I'm using an Apple phone here.
+
+42
+00:01:39,000 --> 00:01:44,000
+And then the price, let's say $1,500.
+
+43
+00:01:44,000 --> 00:01:46,000
+And what else we have? We have a name.
+
+44
+00:01:46,000 --> 00:01:47,000
+So what do you call a mobile phone?
+
+45
+00:01:47,000 --> 00:01:50,000
+So currently, if we talk about Apple phones
+
+46
+00:01:50,000 --> 00:01:54,000
+or any phones nowadays, we call them as a smartphone, okay?
+
+47
+00:01:54,000 --> 00:01:55,000
+I know this variable doesn't make sense,
+
+48
+00:01:55,000 --> 00:01:57,000
+but just for the example,
+
+49
+00:01:57,000 --> 00:02:00,000
+I'm saying name = "SmartPhone", right?
+
+50
+00:02:00,000 --> 00:02:03,000
+Now if you talk about this phone here,
+
+51
+00:02:03,000 --> 00:02:05,000
+we have all these values, right?
+
+52
+00:02:05,000 --> 00:02:09,000
+Now of course, if I create multiple objects,
+
+53
+00:02:09,000 --> 00:02:10,000
+it should have a different value.
+
+54
+00:02:10,000 --> 00:02:11,000
+Of course, every object is different,
+
+55
+00:02:11,000 --> 00:02:13,000
+so we can have a different value to it.
+
+56
+00:02:13,000 --> 00:02:14,000
+If I come back to Apple,
+
+57
+00:02:14,000 --> 00:02:17,000
+let's say the next phone is of Samsung,
+
+58
+00:02:17,000 --> 00:02:20,000
+and the price is let's say $1,700.
+
+59
+00:02:20,000 --> 00:02:24,000
+And then we also call them as SmartPhone, okay?
+
+60
+00:02:24,000 --> 00:02:25,000
+The only thing that we have to change it here
+
+61
+00:02:25,000 --> 00:02:27,000
+as well, obj2, obj2,
+
+62
+00:02:27,000 --> 00:02:30,000
+and then I can print the values as well.
+
+63
+00:02:30,000 --> 00:02:31,000
+You know what I will do?
+
+64
+00:02:31,000 --> 00:02:33,000
+I will just create a method which will print everything.
+
+65
+00:02:33,000 --> 00:02:34,000
+I will say public void show.
+
+66
+00:02:34,000 --> 00:02:36,000
+It should print all the details here.
+
+67
+00:02:36,000 --> 00:02:39,000
+So it should print brand so that I don't have
+
+68
+00:02:39,000 --> 00:02:41,000
+to print that every time,
+
+69
+00:02:41,000 --> 00:02:45,000
+and I will say price, and I will print name as well.
+
+70
+00:02:45,000 --> 00:02:45,000
+Now by doing this,
+
+71
+00:02:45,000 --> 00:02:49,000
+what I'm doing is instead of printing it here every value,
+
+72
+00:02:49,000 --> 00:02:53,000
+I can simply call obj1.show do show and obj2.show.
+
+73
+00:02:53,000 --> 00:02:56,000
+So it'll print its own value, not other values.
+
+74
+00:02:56,000 --> 00:03:00,000
+And if I come back here, compile and run,
+
+75
+00:03:00,000 --> 00:03:01,000
+you can see we got the values, right?
+
+76
+00:03:01,000 --> 00:03:02,000
+Nothing complex here.
+
+77
+00:03:02,000 --> 00:03:05,000
+The thing is if we talk about these variables here,
+
+78
+00:03:05,000 --> 00:03:07,000
+they are called instance variable, right?
+
+79
+00:03:07,000 --> 00:03:08,000
+Now if you create a variable inside a method,
+
+80
+00:03:08,000 --> 00:03:10,000
+that's a local variable.
+
+81
+00:03:10,000 --> 00:03:12,000
+But this are your instance variable,
+
+82
+00:03:12,000 --> 00:03:14,000
+and every variable
+
+83
+00:03:14,000 --> 00:03:16,000
+for a particular object is different, right?
+
+84
+00:03:16,000 --> 00:03:17,000
+The value will be different.
+
+85
+00:03:17,000 --> 00:03:21,000
+Now what I want is I want to have the name
+
+86
+00:03:21,000 --> 00:03:23,000
+to be same for all the objects.
+
+87
+00:03:23,000 --> 00:03:25,000
+See, because what is happening is in your memory,
+
+88
+00:03:25,000 --> 00:03:27,000
+so let's say we have a JVM, a big JVM,
+
+89
+00:03:27,000 --> 00:03:30,000
+and inside this, you have a stack
+
+90
+00:03:30,000 --> 00:03:34,000
+where you have all the reference and locations and address,
+
+91
+00:03:34,000 --> 00:03:35,000
+and then you have a heap memory.
+
+92
+00:03:35,000 --> 00:03:38,000
+So in total, you can see we got two objects, right?
+
+93
+00:03:38,000 --> 00:03:43,000
+One with Mobile obj1 and one is obj2,
+
+94
+00:03:43,000 --> 00:03:45,000
+and then of course, they have the address as well.
+
+95
+00:03:45,000 --> 00:03:47,000
+So this is 101, 103.
+
+96
+00:03:47,000 --> 00:03:51,000
+And of course, this will be 101, 103,
+
+97
+00:03:51,000 --> 00:03:52,000
+and you will be referring that, right?
+
+98
+00:03:52,000 --> 00:03:55,000
+So this is for that here, this is for that here.
+
+99
+00:03:55,000 --> 00:03:57,000
+Now that's how we can basically use it,
+
+100
+00:03:57,000 --> 00:03:59,000
+and every object will have a different value.
+
+101
+00:03:59,000 --> 00:04:01,000
+But what if I want
+
+102
+00:04:01,000 --> 00:04:03,000
+to have a common value for all the objects?
+
+103
+00:04:03,000 --> 00:04:06,000
+The problem with this is if I want to make sure
+
+104
+00:04:06,000 --> 00:04:08,000
+that the name variable should not be a part of the object,
+
+105
+00:04:08,000 --> 00:04:09,000
+because that's an instance variable.
+
+106
+00:04:09,000 --> 00:04:11,000
+Now it will have a part of the object,
+
+107
+00:04:11,000 --> 00:04:13,000
+and every object will have a different value.
+
+108
+00:04:13,000 --> 00:04:17,000
+I want this name to be common for all. How do I do that?
+
+109
+00:04:17,000 --> 00:04:22,000
+Now if you make this variable as static, now by doing that,
+
+110
+00:04:22,000 --> 00:04:26,000
+what we are doing is we are making this name variable common
+
+111
+00:04:26,000 --> 00:04:28,000
+to all the object.
+
+112
+00:04:28,000 --> 00:04:31,000
+What I mean by that is, let's say after sometime,
+
+113
+00:04:31,000 --> 00:04:34,000
+if I say obj1.name.
+
+114
+00:04:34,000 --> 00:04:37,000
+If I change the name to let's say a Phone here,
+
+115
+00:04:37,000 --> 00:04:39,000
+just a Phone, not a SmartPhone anymore.
+
+116
+00:04:39,000 --> 00:04:42,000
+If you make this as a Phone and if you see the values,
+
+117
+00:04:42,000 --> 00:04:46,000
+it will affect all the objects.
+
+118
+00:04:46,000 --> 00:04:49,000
+You can see we are trying to change the name of obj1,
+
+119
+00:04:49,000 --> 00:04:54,000
+but we are actually changing the name of obj2 as well.
+
+120
+00:04:54,000 --> 00:04:56,000
+You can see this is also Phone now.
+
+121
+00:04:56,000 --> 00:04:59,000
+The reason is the static variable is actually shared
+
+122
+00:04:59,000 --> 00:05:01,000
+by all the objects.
+
+123
+00:05:01,000 --> 00:05:03,000
+So basically, we'll not be having individual static variable
+
+124
+00:05:03,000 --> 00:05:05,000
+for every object.
+
+125
+00:05:05,000 --> 00:05:06,000
+We have a common variable,
+
+126
+00:05:06,000 --> 00:05:08,000
+which will be used by all the objects.
+
+127
+00:05:08,000 --> 00:05:11,000
+Imagine there is a common variable here, name,
+
+128
+00:05:11,000 --> 00:05:14,000
+and all the objects will be referring to the same variable.
+
+129
+00:05:14,000 --> 00:05:16,000
+So if you change the value for this,
+
+130
+00:05:16,000 --> 00:05:19,000
+it will affect all the objects, okay?
+
+131
+00:05:19,000 --> 00:05:22,000
+Now this is why we use static.
+
+132
+00:05:22,000 --> 00:05:24,000
+Now the beauty is see,
+
+133
+00:05:24,000 --> 00:05:26,000
+why we have to refer brand with obj1,
+
+134
+00:05:26,000 --> 00:05:27,000
+price with obj1 is
+
+135
+00:05:27,000 --> 00:05:31,000
+because every object will have a different value for it.
+
+136
+00:05:31,000 --> 00:05:34,000
+Now don't you think name is a static variable,
+
+137
+00:05:34,000 --> 00:05:37,000
+and it will be common for all the objects?
+
+138
+00:05:37,000 --> 00:05:40,000
+And that's why you can actually call name
+
+139
+00:05:40,000 --> 00:05:43,000
+with the help of a class name itself.
+
+140
+00:05:43,000 --> 00:05:45,000
+You can simply say Mobile.name.
+
+141
+00:05:45,000 --> 00:05:47,000
+So static variables should be called
+
+142
+00:05:47,000 --> 00:05:50,000
+with their class name, not with objects.
+
+143
+00:05:50,000 --> 00:05:53,000
+You can call with objects, but avoid it.
+
+144
+00:05:53,000 --> 00:05:55,000
+And that's why you can see it gives you warning as well.
+
+145
+00:05:55,000 --> 00:05:58,000
+It says, "The static field Mobile.name should be accessed
+
+146
+00:05:58,000 --> 00:06:03,000
+in a static way," which is using the class name,
+
+147
+00:06:03,000 --> 00:06:05,000
+which is mobile, okay?
+
+148
+00:06:05,000 --> 00:06:06,000
+So the point
+
+149
+00:06:06,000 --> 00:06:09,000
+to remember here is static variables are actually shared
+
+150
+00:06:09,000 --> 00:06:11,000
+by different objects,
+
+151
+00:06:11,000 --> 00:06:13,000
+and if you want to refer to a static variable,
+
+152
+00:06:13,000 --> 00:06:14,000
+you can use a class name.
+
+153
+00:06:14,000 --> 00:06:17,000
+So there's a different area in your JVM
+
+154
+00:06:17,000 --> 00:06:19,000
+where you have all the static variables.
+
+155
+00:06:19,000 --> 00:06:22,000
+And here as well, I should say Mobile.
+
+156
+00:06:22,000 --> 00:06:24,000
+Now the thing is in non-static methods,
+
+157
+00:06:24,000 --> 00:06:26,000
+you can use static variables.
+
+158
+00:06:26,000 --> 00:06:30,000
+There's no harm, okay? And that's a point to remember.
+
+159
+00:06:30,000 --> 00:06:31,000
+In the next video,
+
+160
+00:06:31,000 --> 00:06:33,000
+we'll talk about what if you create a static method?
+
+161
+00:06:33,000 --> 00:06:35,000
+Yes, we can do that. We can create static method.
+
+162
+00:06:35,000 --> 00:06:38,000
+And the question is, can I use instance variables there?
+
+163
+00:06:38,000 --> 00:06:40,000
+Okay, we'll see that in the next video.
+
+164
+00:06:40,000 --> 00:06:44,000
+But here, we talked about what is a static keyword.
+
+165
+00:06:44,000 --> 00:06:47,000
+So static keyword means you are making something
+
+166
+00:06:47,000 --> 00:06:49,000
+as a class member, not a object member.
+
+167
+00:06:49,000 --> 00:06:52,000
+So static, this name here belongs to a class,
+
+168
+00:06:52,000 --> 00:06:53,000
+not to the object,
+
+169
+00:06:53,000 --> 00:06:55,000
+and that's why you were able to use this
+
+170
+00:06:55,000 --> 00:06:58,000
+with the help of a class name, okay?
+
+171
+00:06:58,000 --> 00:07:00,000
+And then you're saving memory as well
+
+172
+00:07:00,000 --> 00:07:03,000
+because not every object will have their own value for it
+
+173
+00:07:03,000 --> 00:07:05,000
+or their own copy for it.
+
+174
+00:07:05,000 --> 00:07:06,000
+So that's about static variable.
+
+175
+00:07:06,000 --> 00:07:09,000
+In the next video, we'll talk about static methods.
+
diff --git a/02 - Core Java/042 Source-code.url b/02 - Core Java/042 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/042 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/042 Static method_en.srt b/02 - Core Java/042 Static method_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..79a75ed8559372f5bc517a73bd8fd94c8b895cbb
--- /dev/null
+++ b/02 - Core Java/042 Static method_en.srt	
@@ -0,0 +1,508 @@
+1
+00:00:03,000 --> 00:00:05,000
+-: Now once we talked about static variable,
+
+2
+00:00:05,000 --> 00:00:07,000
+it's time to talk about static methods.
+
+3
+00:00:07,000 --> 00:00:08,000
+Now what I will do is
+
+4
+00:00:08,000 --> 00:00:11,000
+I will just try to remove all this content from here
+
+5
+00:00:11,000 --> 00:00:13,000
+just to keep it simple
+
+6
+00:00:13,000 --> 00:00:16,000
+and let's make a static method.
+
+7
+00:00:16,000 --> 00:00:17,000
+Now, the method which we have here show
+
+8
+00:00:17,000 --> 00:00:19,000
+is not a static method, right?
+
+9
+00:00:19,000 --> 00:00:20,000
+It's a instance method,
+
+10
+00:00:20,000 --> 00:00:23,000
+is because we have not mentioned a static keyword.
+
+11
+00:00:23,000 --> 00:00:27,000
+Now, whenever you want to work with a non-static method,
+
+12
+00:00:27,000 --> 00:00:29,000
+you need to create an object of it.
+
+13
+00:00:29,000 --> 00:00:30,000
+Of course, if you want to call,
+
+14
+00:00:30,000 --> 00:00:33,000
+you have to create object of mobile.
+
+15
+00:00:33,000 --> 00:00:36,000
+In fact, you know, actually we need those objects here
+
+16
+00:00:36,000 --> 00:00:40,000
+and let's keep it here just to use it.
+
+17
+00:00:40,000 --> 00:00:42,000
+Now let me create a simple static method.
+
+18
+00:00:42,000 --> 00:00:47,000
+So I will say public static void show1.
+
+19
+00:00:48,000 --> 00:00:49,000
+Again, if you can see,
+
+20
+00:00:49,000 --> 00:00:52,000
+I'm using a different method name just to differentiate it.
+
+21
+00:00:52,000 --> 00:00:54,000
+And here, if I try to,
+
+22
+00:00:54,000 --> 00:00:58,000
+first of all, I will just print in static method.
+
+23
+00:00:59,000 --> 00:01:01,000
+Now, how do we call the static method?
+
+24
+00:01:01,000 --> 00:01:04,000
+To call show, we have to get object, right?
+
+25
+00:01:04,000 --> 00:01:08,000
+You can't simply come back here and say, mobile.show,
+
+26
+00:01:08,000 --> 00:01:09,000
+this will not work.
+
+27
+00:01:09,000 --> 00:01:11,000
+If you try to call mobile.show,
+
+28
+00:01:11,000 --> 00:01:12,000
+it'll give you an error.
+
+29
+00:01:12,000 --> 00:01:13,000
+It says,
+
+30
+00:01:13,000 --> 00:01:14,000
+let's see the error.
+
+31
+00:01:14,000 --> 00:01:15,000
+It says cannot make a static reference
+
+32
+00:01:15,000 --> 00:01:17,000
+to a non-static method.
+
+33
+00:01:17,000 --> 00:01:19,000
+That means you cannot call a non-static method
+
+34
+00:01:19,000 --> 00:01:20,000
+with the help of a class name.
+
+35
+00:01:20,000 --> 00:01:23,000
+And that's why you need object here, which you can see.
+
+36
+00:01:23,000 --> 00:01:24,000
+We are using obj1, obj2 .
+
+37
+00:01:25,000 --> 00:01:28,000
+But can I call show one from mobile?
+
+38
+00:01:28,000 --> 00:01:29,000
+Let's try, and we can.
+
+39
+00:01:29,000 --> 00:01:32,000
+You can see that there's no problem.
+
+40
+00:01:32,000 --> 00:01:34,000
+So you can call a static method
+
+41
+00:01:34,000 --> 00:01:36,000
+directly with the help of a class name.
+
+42
+00:01:36,000 --> 00:01:37,000
+That's what we are doing here.
+
+43
+00:01:37,000 --> 00:01:39,000
+We're directly calling it with a class name.
+
+44
+00:01:39,000 --> 00:01:41,000
+Now the question is,
+
+45
+00:01:41,000 --> 00:01:41,000
+this looks cool, right?
+
+46
+00:01:41,000 --> 00:01:44,000
+Static method can be used directly with a class name,
+
+47
+00:01:44,000 --> 00:01:46,000
+but can I use a variables here?
+
+48
+00:01:46,000 --> 00:01:48,000
+Let's try to do the same thing.
+
+49
+00:01:48,000 --> 00:01:51,000
+I will just copy this line and paste it here.
+
+50
+00:01:51,000 --> 00:01:52,000
+Let's see what happens.
+
+51
+00:01:52,000 --> 00:01:54,000
+The moment you do that,
+
+52
+00:01:54,000 --> 00:01:55,000
+you can say there's no problem with name.
+
+53
+00:01:55,000 --> 00:01:58,000
+So that means you can use a static variable
+
+54
+00:01:58,000 --> 00:02:00,000
+inside a static method,
+
+55
+00:02:00,000 --> 00:02:03,000
+but you cannot use a non-static variable
+
+56
+00:02:03,000 --> 00:02:06,000
+inside a static method.
+
+57
+00:02:06,000 --> 00:02:08,000
+The question is why?
+
+58
+00:02:08,000 --> 00:02:10,000
+I mean, think about this,
+
+59
+00:02:10,000 --> 00:02:12,000
+brand and price they instance variable.
+
+60
+00:02:12,000 --> 00:02:14,000
+That means it'll be different for different objects.
+
+61
+00:02:14,000 --> 00:02:16,000
+Now, when you call show with obj1,
+
+62
+00:02:16,000 --> 00:02:17,000
+we know that in this show
+
+63
+00:02:17,000 --> 00:02:19,000
+when you are printing brand and price,
+
+64
+00:02:19,000 --> 00:02:21,000
+you're talking about obj1.
+
+65
+00:02:21,000 --> 00:02:23,000
+When you call show with obj2,
+
+66
+00:02:23,000 --> 00:02:27,000
+you know that the brand and price will be of obj2.
+
+67
+00:02:27,000 --> 00:02:29,000
+But then when you call mobile.show1,
+
+68
+00:02:29,000 --> 00:02:33,000
+how do we know which object you're referring to?
+
+69
+00:02:33,000 --> 00:02:36,000
+So this brand belongs to obj1 or it belongs to obj2
+
+70
+00:02:36,000 --> 00:02:37,000
+and that's why it says,
+
+71
+00:02:37,000 --> 00:02:39,000
+hey, there's a confusion, right?
+
+72
+00:02:39,000 --> 00:02:40,000
+Let's not do that.
+
+73
+00:02:40,000 --> 00:02:42,000
+Let's not have a non-static variable
+
+74
+00:02:42,000 --> 00:02:45,000
+directly getting access in a static method.
+
+75
+00:02:45,000 --> 00:02:46,000
+It's not possible.
+
+76
+00:02:46,000 --> 00:02:48,000
+This time I added a directly keyword that
+
+77
+00:02:48,000 --> 00:02:50,000
+that means indirectly is possible.
+
+78
+00:02:50,000 --> 00:02:51,000
+Now, how will you do the indirectly?
+
+79
+00:02:51,000 --> 00:02:52,000
+It's very simple.
+
+80
+00:02:52,000 --> 00:02:56,000
+What if you can actually pass the object itself?
+
+81
+00:02:56,000 --> 00:02:57,000
+You can say,
+
+82
+00:02:57,000 --> 00:03:00,000
+hey, I want to run show 1 for obj1 object.
+
+83
+00:03:01,000 --> 00:03:02,000
+Now, since you are passing the object,
+
+84
+00:03:02,000 --> 00:03:04,000
+you have to also accept it here.
+
+85
+00:03:04,000 --> 00:03:07,000
+So it can say mobile obj.
+
+86
+00:03:07,000 --> 00:03:10,000
+And now, now since we have the object,
+
+87
+00:03:10,000 --> 00:03:13,000
+I can refer that with the help of obj1.brand,
+
+88
+00:03:13,000 --> 00:03:16,000
+I mean, obj.brand on obj.prize.
+
+89
+00:03:16,000 --> 00:03:19,000
+So basically we cannot directly use a non-static variable
+
+90
+00:03:19,000 --> 00:03:21,000
+inside a static method.
+
+91
+00:03:21,000 --> 00:03:23,000
+But if you have object reference, then you can use it.
+
+92
+00:03:23,000 --> 00:03:25,000
+Because now we can differentiate.
+
+93
+00:03:25,000 --> 00:03:26,000
+So the brand which I'm talking about
+
+94
+00:03:26,000 --> 00:03:28,000
+is for obj1, not for obj2.
+
+95
+00:03:28,000 --> 00:03:29,000
+So that's how we have to do it.
+
+96
+00:03:29,000 --> 00:03:31,000
+So that's how we work with static method.
+
+97
+00:03:31,000 --> 00:03:33,000
+Now, if you observe here,
+
+98
+00:03:33,000 --> 00:03:34,000
+from start we are using this, right?
+
+99
+00:03:34,000 --> 00:03:37,000
+The main method is static.
+
+100
+00:03:37,000 --> 00:03:39,000
+Why in this world we have a main static?
+
+101
+00:03:39,000 --> 00:03:42,000
+Is because if you don't make main static,
+
+102
+00:03:42,000 --> 00:03:43,000
+if this was a syntax,
+
+103
+00:03:43,000 --> 00:03:46,000
+the problem is if you don't mention static,
+
+104
+00:03:46,000 --> 00:03:50,000
+that means main becomes a non-static method,
+
+105
+00:03:50,000 --> 00:03:53,000
+which means if you want to call main,
+
+106
+00:03:53,000 --> 00:03:55,000
+we have to first create the object of demo.
+
+107
+00:03:55,000 --> 00:03:57,000
+Oh, that means you cannot call main
+
+108
+00:03:57,000 --> 00:03:59,000
+without the object of demo.
+
+109
+00:03:59,000 --> 00:04:01,000
+But the question is, we all know
+
+110
+00:04:01,000 --> 00:04:04,000
+that main is a starting point of execution.
+
+111
+00:04:04,000 --> 00:04:07,000
+If the execution has not started,
+
+112
+00:04:07,000 --> 00:04:08,000
+how can you create object of demo?
+
+113
+00:04:08,000 --> 00:04:11,000
+Okay, so if there's a deadlock here, right?
+
+114
+00:04:11,000 --> 00:04:13,000
+So to solve that problem, what we can do is
+
+115
+00:04:13,000 --> 00:04:15,000
+we can make this variable as static.
+
+116
+00:04:15,000 --> 00:04:17,000
+The moment you do that, we are saying,
+
+117
+00:04:17,000 --> 00:04:18,000
+hey, you know what?
+
+118
+00:04:18,000 --> 00:04:22,000
+To call main we don't need object of demo.
+
+119
+00:04:22,000 --> 00:04:24,000
+Problem solved, right?
+
+120
+00:04:24,000 --> 00:04:26,000
+So yeah, this is how we can solve this problem
+
+121
+00:04:26,000 --> 00:04:30,000
+and this is what static methods are.
+
+122
+00:04:30,000 --> 00:04:31,000
+Anything else?
+
+123
+00:04:31,000 --> 00:04:33,000
+Actually, I think we, it looks good.
+
+124
+00:04:33,000 --> 00:04:35,000
+In the next video, let's try to see
+
+125
+00:04:35,000 --> 00:04:37,000
+something more about static.
+
+126
+00:04:37,000 --> 00:04:39,000
+There's a concept of static block,
+
+127
+00:04:39,000 --> 00:04:41,000
+which we'll discuss in the next video.
+
diff --git a/02 - Core Java/043 Source-code.url b/02 - Core Java/043 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/043 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/043 Static block_en.srt b/02 - Core Java/043 Static block_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..b0a475dff758cbe661b906350311a51750a4f59d
--- /dev/null
+++ b/02 - Core Java/043 Static block_en.srt	
@@ -0,0 +1,800 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle piano music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: Now we know what is static variables,
+
+3
+00:00:05,000 --> 00:00:06,000
+static methods, right?
+
+4
+00:00:06,000 --> 00:00:08,000
+Now let's try to expand this more.
+
+5
+00:00:08,000 --> 00:00:09,000
+To simplify this,
+
+6
+00:00:09,000 --> 00:00:10,000
+what I will do is I will remove the static method
+
+7
+00:00:10,000 --> 00:00:11,000
+for some time
+
+8
+00:00:11,000 --> 00:00:14,000
+and I will also decrease this code.
+
+9
+00:00:14,000 --> 00:00:16,000
+Let's only work with one object now.
+
+10
+00:00:16,000 --> 00:00:20,000
+And here, see, normally when you work with variables,
+
+11
+00:00:20,000 --> 00:00:23,000
+so we know that this is an instance variable,
+
+12
+00:00:23,000 --> 00:00:26,000
+and this is a static variable, right, the name.
+
+13
+00:00:26,000 --> 00:00:29,000
+Now to instantiate the instance variable,
+
+14
+00:00:29,000 --> 00:00:29,000
+what do we do?
+
+15
+00:00:29,000 --> 00:00:33,000
+Of course we can instantiate the variables from here,
+
+16
+00:00:33,000 --> 00:00:34,000
+but then what if you want
+
+17
+00:00:34,000 --> 00:00:36,000
+to instantiate the variable on this line,
+
+18
+00:00:36,000 --> 00:00:37,000
+if you want to give some value?
+
+19
+00:00:37,000 --> 00:00:39,000
+Not instantiate, if you want to initialize the variable,
+
+20
+00:00:39,000 --> 00:00:40,000
+what you will do?
+
+21
+00:00:40,000 --> 00:00:42,000
+So basically we have seen one concept,
+
+22
+00:00:42,000 --> 00:00:43,000
+right, which is constructor.
+
+23
+00:00:43,000 --> 00:00:48,000
+So using constructor, we can say, okay, public Mobile,
+
+24
+00:00:49,000 --> 00:00:51,000
+and we can give some default values to it, right?
+
+25
+00:00:51,000 --> 00:00:53,000
+So by default, the brand will be empty string,
+
+26
+00:00:53,000 --> 00:00:55,000
+and by default the price will be,
+
+27
+00:00:55,000 --> 00:00:57,000
+let's say $200, right?
+
+28
+00:00:57,000 --> 00:01:01,000
+So this is the default brand, default text,
+
+29
+00:01:01,000 --> 00:01:02,000
+and default number, right?
+
+30
+00:01:02,000 --> 00:01:03,000
+Which we want to give.
+
+31
+00:01:03,000 --> 00:01:04,000
+What about name?
+
+32
+00:01:04,000 --> 00:01:06,000
+I can also give a default name to a name,
+
+33
+00:01:06,000 --> 00:01:09,000
+which is phone in this case, let's say.
+
+34
+00:01:09,000 --> 00:01:10,000
+And we can do that.
+
+35
+00:01:10,000 --> 00:01:12,000
+We can initialize the static variable
+
+36
+00:01:12,000 --> 00:01:13,000
+inside a constructor,
+
+37
+00:01:13,000 --> 00:01:14,000
+and there's no harm in that.
+
+38
+00:01:14,000 --> 00:01:19,000
+Now the problem is every time you create an object,
+
+39
+00:01:19,000 --> 00:01:20,000
+every time you create one more object,
+
+40
+00:01:20,000 --> 00:01:22,000
+it'll call the construct, right?
+
+41
+00:01:22,000 --> 00:01:24,000
+And don't you think it makes sense for this tool
+
+42
+00:01:24,000 --> 00:01:26,000
+to initialize every time,
+
+43
+00:01:26,000 --> 00:01:29,000
+but why name has to initialize every time?
+
+44
+00:01:29,000 --> 00:01:32,000
+I feel that the name variable, which is static,
+
+45
+00:01:32,000 --> 00:01:34,000
+should be initialized only once.
+
+46
+00:01:34,000 --> 00:01:34,000
+What do you feel?
+
+47
+00:01:34,000 --> 00:01:36,000
+Of course the same thing, right?
+
+48
+00:01:36,000 --> 00:01:37,000
+How will you do that?
+
+49
+00:01:37,000 --> 00:01:38,000
+So if you mention that here,
+
+50
+00:01:38,000 --> 00:01:40,000
+of course every time you call the constructor,
+
+51
+00:01:40,000 --> 00:01:41,000
+it will initialize.
+
+52
+00:01:41,000 --> 00:01:42,000
+We don't wanna do that.
+
+53
+00:01:42,000 --> 00:01:43,000
+Now to achieve that,
+
+54
+00:01:43,000 --> 00:01:47,000
+we have a special block called a static block.
+
+55
+00:01:47,000 --> 00:01:48,000
+Now, in the static block,
+
+56
+00:01:48,000 --> 00:01:52,000
+we can basically initialize the variable,
+
+57
+00:01:52,000 --> 00:01:53,000
+the static variable.
+
+58
+00:01:53,000 --> 00:01:54,000
+Now the good thing
+
+59
+00:01:54,000 --> 00:01:57,000
+about this is the static block will be called only once.
+
+60
+00:01:57,000 --> 00:02:00,000
+Irrespective how many objects you create,
+
+61
+00:02:00,000 --> 00:02:02,000
+it'll call the static block only once.
+
+62
+00:02:02,000 --> 00:02:04,000
+So what I will do is just to demonstrate
+
+63
+00:02:04,000 --> 00:02:08,000
+that I will create one more object here, let's say.
+
+64
+00:02:08,000 --> 00:02:09,000
+And I will not assign any value to it,
+
+65
+00:02:09,000 --> 00:02:14,000
+just to default values obj2, second object.
+
+66
+00:02:14,000 --> 00:02:16,000
+So it'll call the constructor two times.
+
+67
+00:02:16,000 --> 00:02:19,000
+It'll call the static block only once.
+
+68
+00:02:19,000 --> 00:02:19,000
+To prove that,
+
+69
+00:02:19,000 --> 00:02:21,000
+what I will do is I will just print something.
+
+70
+00:02:21,000 --> 00:02:24,000
+I will say in static block.
+
+71
+00:02:24,000 --> 00:02:25,000
+Now the syntax for static block is very simple.
+
+72
+00:02:25,000 --> 00:02:27,000
+It's static keyword,
+
+73
+00:02:27,000 --> 00:02:29,000
+and then you just open and close.
+
+74
+00:02:29,000 --> 00:02:30,000
+There's no bracket or something.
+
+75
+00:02:30,000 --> 00:02:33,000
+It's just a simple block, okay?
+
+76
+00:02:33,000 --> 00:02:33,000
+And in the constructor as well,
+
+77
+00:02:33,000 --> 00:02:38,000
+I will say in constructor, okay?
+
+78
+00:02:38,000 --> 00:02:42,000
+And now with this, let me just compile this code, okay?
+
+79
+00:02:42,000 --> 00:02:43,000
+There is an issue.
+
+80
+00:02:43,000 --> 00:02:45,000
+I have returned one extra, okay.
+
+81
+00:02:45,000 --> 00:02:49,000
+I have removed the curly brackets from here.
+
+82
+00:02:49,000 --> 00:02:52,000
+So compile and run.
+
+83
+00:02:52,000 --> 00:02:54,000
+So you can see it is calling the static block only once,
+
+84
+00:02:54,000 --> 00:02:57,000
+and it's calling constructor two times.
+
+85
+00:02:57,000 --> 00:02:58,000
+There's one more issue,
+
+86
+00:02:58,000 --> 00:03:01,000
+why static block is called first
+
+87
+00:03:01,000 --> 00:03:03,000
+even before the constructor is calling static block.
+
+88
+00:03:03,000 --> 00:03:04,000
+And that's weird.
+
+89
+00:03:04,000 --> 00:03:05,000
+Is it the sequence?
+
+90
+00:03:05,000 --> 00:03:07,000
+Let's try, let me just put this
+
+91
+00:03:07,000 --> 00:03:09,000
+after the constructor.
+
+92
+00:03:09,000 --> 00:03:11,000
+Let's see if it doesn't make any sense.
+
+93
+00:03:11,000 --> 00:03:13,000
+Anyway, Java does not follow the sequence.
+
+94
+00:03:13,000 --> 00:03:16,000
+But just to confirm,
+
+95
+00:03:16,000 --> 00:03:20,000
+you can see the static block is still getting called first.
+
+96
+00:03:20,000 --> 00:03:23,000
+Now to understand that, let's go to the diagram here.
+
+97
+00:03:23,000 --> 00:03:24,000
+See what happens.
+
+98
+00:03:24,000 --> 00:03:26,000
+There are two words,
+
+99
+00:03:26,000 --> 00:03:27,000
+and we only focus on one word.
+
+100
+00:03:27,000 --> 00:03:30,000
+Every time you get the object, that two steps,
+
+101
+00:03:30,000 --> 00:03:34,000
+one, your class loads,
+
+102
+00:03:35,000 --> 00:03:39,000
+and then your objects are, okay,
+
+103
+00:03:39,000 --> 00:03:40,000
+so first your class loads
+
+104
+00:03:40,000 --> 00:03:42,000
+and then your object gets instantiated.
+
+105
+00:03:42,000 --> 00:03:44,000
+So there are two steps.
+
+106
+00:03:44,000 --> 00:03:46,000
+Every time you create the object,
+
+107
+00:03:46,000 --> 00:03:48,000
+there are two steps, class loads
+
+108
+00:03:48,000 --> 00:03:50,000
+and object will then will get initialized.
+
+109
+00:03:50,000 --> 00:03:53,000
+The thing is, the class will load only once.
+
+110
+00:03:53,000 --> 00:03:57,000
+So basically in your JVM, you have a special area here,
+
+111
+00:03:57,000 --> 00:04:00,000
+which is called a class loader, okay?
+
+112
+00:04:00,000 --> 00:04:03,000
+And this will have all the class which are loaded.
+
+113
+00:04:03,000 --> 00:04:04,000
+And by default, of course you don't have
+
+114
+00:04:04,000 --> 00:04:05,000
+any class loaded, right?
+
+115
+00:04:05,000 --> 00:04:09,000
+So the class will get loaded from your library
+
+116
+00:04:09,000 --> 00:04:11,000
+to the class loader.
+
+117
+00:04:11,000 --> 00:04:13,000
+And it'll happen only once.
+
+118
+00:04:13,000 --> 00:04:15,000
+So for the first object, when it sees, "Hey,
+
+119
+00:04:15,000 --> 00:04:18,000
+this object creation, it'll load the class first,"
+
+120
+00:04:18,000 --> 00:04:20,000
+and then it'll create the object.
+
+121
+00:04:20,000 --> 00:04:22,000
+Now, every time you load a class,
+
+122
+00:04:22,000 --> 00:04:25,000
+it'll call the static block.
+
+123
+00:04:25,000 --> 00:04:27,000
+Now, since class loading happens first,
+
+124
+00:04:27,000 --> 00:04:29,000
+and that's why it'll call the static block first,
+
+125
+00:04:29,000 --> 00:04:31,000
+and then it'll create the object.
+
+126
+00:04:31,000 --> 00:04:34,000
+And that's why it'll call the constructor
+
+127
+00:04:34,000 --> 00:04:36,000
+after static block.
+
+128
+00:04:36,000 --> 00:04:38,000
+Now, irrespective of how many objects you create,
+
+129
+00:04:38,000 --> 00:04:40,000
+the class is already loaded, right?
+
+130
+00:04:40,000 --> 00:04:42,000
+So you can simply create the next object
+
+131
+00:04:42,000 --> 00:04:43,000
+without loading because it's already loaded.
+
+132
+00:04:43,000 --> 00:04:46,000
+Now my question is, if that is how it is working,
+
+133
+00:04:46,000 --> 00:04:48,000
+what if I don't create any object?
+
+134
+00:04:48,000 --> 00:04:50,000
+I'm not getting any object now.
+
+135
+00:04:50,000 --> 00:04:52,000
+So if you don't create the object,
+
+136
+00:04:52,000 --> 00:04:54,000
+of course it'll not call the constructor.
+
+137
+00:04:54,000 --> 00:04:55,000
+But what about static block?
+
+138
+00:04:55,000 --> 00:04:57,000
+It'll not even call the static block.
+
+139
+00:04:57,000 --> 00:05:00,000
+If you can see, we don't have any output, oh, okay.
+
+140
+00:05:00,000 --> 00:05:02,000
+So that means if you don't create the object,
+
+141
+00:05:02,000 --> 00:05:05,000
+it'll not load the class as well.
+
+142
+00:05:05,000 --> 00:05:06,000
+But what if you wanna do that?
+
+143
+00:05:06,000 --> 00:05:10,000
+What if you want to load the class?
+
+144
+00:05:10,000 --> 00:05:11,000
+How would you do that?
+
+145
+00:05:11,000 --> 00:05:14,000
+Now for that, we have a special class inside Java,
+
+146
+00:05:14,000 --> 00:05:16,000
+which is called a Class class.
+
+147
+00:05:16,000 --> 00:05:17,000
+Yeah, that's a class.
+
+148
+00:05:17,000 --> 00:05:20,000
+Okay, I know Java has been weird.
+
+149
+00:05:20,000 --> 00:05:22,000
+We have Object class, we have Class class,
+
+150
+00:05:22,000 --> 00:05:23,000
+but that's how it is designed.
+
+151
+00:05:23,000 --> 00:05:26,000
+So Java Class, if you go there,
+
+152
+00:05:26,000 --> 00:05:29,000
+you can see it's a class and it has a lot of methods to it.
+
+153
+00:05:29,000 --> 00:05:32,000
+One of the methods which we want to use here is forName.
+
+154
+00:05:32,000 --> 00:05:36,000
+Now forName is a method which does one thing
+
+155
+00:05:36,000 --> 00:05:38,000
+which loads your class.
+
+156
+00:05:38,000 --> 00:05:40,000
+And you just have to mention your class name.
+
+157
+00:05:40,000 --> 00:05:41,000
+What's the class name?
+
+158
+00:05:41,000 --> 00:05:43,000
+Well, the class name is Mobile.
+
+159
+00:05:43,000 --> 00:05:44,000
+So in this you can mention the class name.
+
+160
+00:05:44,000 --> 00:05:46,000
+That's it, okay?
+
+161
+00:05:46,000 --> 00:05:48,000
+The only problem is it throws an exception, okay?
+
+162
+00:05:48,000 --> 00:05:50,000
+At this point we have not talked about exception,
+
+163
+00:05:50,000 --> 00:05:52,000
+but just ignore this line.
+
+164
+00:05:52,000 --> 00:05:55,000
+We'll talk about this in detail later once we start
+
+165
+00:05:55,000 --> 00:05:56,000
+with the exception concept.
+
+166
+00:05:56,000 --> 00:05:58,000
+But as of now, just to make it work,
+
+167
+00:05:58,000 --> 00:06:00,000
+I'm just writing this line, ignore it.
+
+168
+00:06:00,000 --> 00:06:04,000
+What's important is the class.forName will load your class.
+
+169
+00:06:04,000 --> 00:06:07,000
+If I go to forName, you can see forName is a method,
+
+170
+00:06:07,000 --> 00:06:08,000
+and it's a static method.
+
+171
+00:06:08,000 --> 00:06:11,000
+So you can call this with a class name.
+
+172
+00:06:12,000 --> 00:06:14,000
+And this particular method,
+
+173
+00:06:15,000 --> 00:06:18,000
+do they have any definition mentioned?
+
+174
+00:06:18,000 --> 00:06:20,000
+Okay, so it says the system class loader is used.
+
+175
+00:06:20,000 --> 00:06:23,000
+So basically it'll load the system class loader
+
+176
+00:06:23,000 --> 00:06:26,000
+to load this class.
+
+177
+00:06:26,000 --> 00:06:28,000
+Okay, so which class, Mobile class.
+
+178
+00:06:28,000 --> 00:06:31,000
+Okay, so now if I just write this line,
+
+179
+00:06:31,000 --> 00:06:32,000
+it'll not create the object,
+
+180
+00:06:32,000 --> 00:06:36,000
+it'll just instantiate it, compile, run.
+
+181
+00:06:36,000 --> 00:06:40,000
+You can see it says a new static block.
+
+182
+00:06:40,000 --> 00:06:42,000
+Okay, that means you're just loading the class.
+
+183
+00:06:42,000 --> 00:06:44,000
+So basically that's how you load your class.
+
+184
+00:06:44,000 --> 00:06:49,000
+You can simply use this line to load your class.
+
+185
+00:06:49,000 --> 00:06:50,000
+Normally when you build a project,
+
+186
+00:06:50,000 --> 00:06:51,000
+you don't actually use this feature.
+
+187
+00:06:51,000 --> 00:06:53,000
+Yes, there are some situation where you use it.
+
+188
+00:06:53,000 --> 00:06:57,000
+Example, when we start with JDBC, we'll talk about this one,
+
+189
+00:06:57,000 --> 00:06:59,000
+but we normally don't use it.
+
+190
+00:06:59,000 --> 00:07:00,000
+I'm just using this just to show you how
+
+191
+00:07:00,000 --> 00:07:02,000
+to call a static block,
+
+192
+00:07:02,000 --> 00:07:03,000
+how to load a class.
+
+193
+00:07:03,000 --> 00:07:05,000
+Okay, I hope this video makes sense
+
+194
+00:07:05,000 --> 00:07:07,000
+where we talked about static block.
+
+195
+00:07:07,000 --> 00:07:11,000
+So static block is used to initialize the static variables.
+
+196
+00:07:11,000 --> 00:07:12,000
+So that's it from this video in which we talked
+
+197
+00:07:12,000 --> 00:07:14,000
+about static block.
+
+198
+00:07:14,000 --> 00:07:16,000
+In the other videos we have talked about static keyword,
+
+199
+00:07:16,000 --> 00:07:18,000
+static variables, static methods,
+
+200
+00:07:18,000 --> 00:07:19,000
+and yeah, that's about static.
+
diff --git a/02 - Core Java/044 Encapsulation_en.srt b/02 - Core Java/044 Encapsulation_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..9f09825f1e86d043db3f51aac11547bd58d24f43
--- /dev/null
+++ b/02 - Core Java/044 Encapsulation_en.srt	
@@ -0,0 +1,1144 @@
+1
+00:00:00,000 --> 00:00:03,000
+(soft music plays)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: In this video, let's talk about Encapsulation.
+
+3
+00:00:05,000 --> 00:00:07,000
+Now I know that's a new term,
+
+4
+00:00:07,000 --> 00:00:09,000
+but when we started with OOPs concept,
+
+5
+00:00:09,000 --> 00:00:12,000
+now Encapsulation is a part of OOPs.
+
+6
+00:00:12,000 --> 00:00:16,000
+So when I say let's implement Object Oriented Programming,
+
+7
+00:00:16,000 --> 00:00:18,000
+so yeah, we have talked about class,
+
+8
+00:00:18,000 --> 00:00:19,000
+we have talked about objects,
+
+9
+00:00:19,000 --> 00:00:21,000
+and the next step is Encapsulation here.
+
+10
+00:00:21,000 --> 00:00:24,000
+Now by word, what Encapsulation means?
+
+11
+00:00:24,000 --> 00:00:25,000
+We have the concept of capsules
+
+12
+00:00:25,000 --> 00:00:28,000
+where we have medicine powder there?
+
+13
+00:00:28,000 --> 00:00:30,000
+So basically we can imagine capsule
+
+14
+00:00:30,000 --> 00:00:34,000
+as something which is keeping it closed, keeping it tight,
+
+15
+00:00:34,000 --> 00:00:37,000
+and no one from the outside world can use it.
+
+16
+00:00:37,000 --> 00:00:39,000
+That makes sense, right?
+
+17
+00:00:39,000 --> 00:00:41,000
+So what we can do here is let's say,
+
+18
+00:00:41,000 --> 00:00:42,000
+let's design a class, okay?
+
+19
+00:00:42,000 --> 00:00:44,000
+And let's name this class as Human.
+
+20
+00:00:44,000 --> 00:00:46,000
+I know we can use different names,
+
+21
+00:00:46,000 --> 00:00:47,000
+but let's go with Human here.
+
+22
+00:00:47,000 --> 00:00:51,000
+And I know we are aliens, but let's say this is Human.
+
+23
+00:00:51,000 --> 00:00:54,000
+Now here, when you have this Human class,
+
+24
+00:00:54,000 --> 00:00:56,000
+a Human will have some parameters, right?
+
+25
+00:00:56,000 --> 00:00:59,000
+Example, if you remember, we have talked about this
+
+26
+00:00:59,000 --> 00:01:01,000
+before, as a Human or as a person,
+
+27
+00:01:01,000 --> 00:01:03,000
+we know a lot of different stuff.
+
+28
+00:01:03,000 --> 00:01:05,000
+So in your mind you have a lot of different concepts
+
+29
+00:01:05,000 --> 00:01:07,000
+or you know a lot of things.
+
+30
+00:01:07,000 --> 00:01:11,000
+Example, you know your name, you know where you stay,
+
+31
+00:01:11,000 --> 00:01:12,000
+you know your favorite actor,
+
+32
+00:01:12,000 --> 00:01:14,000
+you know your favorite trainer.
+
+33
+00:01:14,000 --> 00:01:16,000
+Of course you can name, you can use my name there,
+
+34
+00:01:16,000 --> 00:01:18,000
+but just kidding.
+
+35
+00:01:18,000 --> 00:01:20,000
+So we have different information, right?
+
+36
+00:01:20,000 --> 00:01:21,000
+Now, can you imagine this,
+
+37
+00:01:21,000 --> 00:01:25,000
+that all the information are actually stored in your brain
+
+38
+00:01:25,000 --> 00:01:27,000
+as a variable box?
+
+39
+00:01:27,000 --> 00:01:30,000
+I'm a big fan of Pixel movie, which is,
+
+40
+00:01:30,000 --> 00:01:32,000
+I don't know the exact movie name,
+
+41
+00:01:32,000 --> 00:01:34,000
+but you know, Pac-Man basically eats people
+
+42
+00:01:34,000 --> 00:01:36,000
+and then they become pixels.
+
+43
+00:01:36,000 --> 00:01:40,000
+So you can imagine the data in your mind is cube, okay?
+
+44
+00:01:40,000 --> 00:01:42,000
+And in that box, you have the data.
+
+45
+00:01:42,000 --> 00:01:46,000
+Example, your name is stored in a box, which name Navin,
+
+46
+00:01:46,000 --> 00:01:48,000
+or which name is equal to
+
+47
+00:01:48,000 --> 00:01:50,000
+and in the box will be having a value.
+
+48
+00:01:50,000 --> 00:01:51,000
+For me it's Navin.
+
+49
+00:01:51,000 --> 00:01:53,000
+Let's say, your favorite actor,
+
+50
+00:01:53,000 --> 00:01:56,000
+so you'll be having my favorite actor,
+
+51
+00:01:56,000 --> 00:01:58,000
+and inside the box will be having a value.
+
+52
+00:01:58,000 --> 00:02:02,000
+So what I'm saying is, all the data is stored in your brain
+
+53
+00:02:02,000 --> 00:02:04,000
+in the format of boxes, variables.
+
+54
+00:02:04,000 --> 00:02:07,000
+Now of course you can use these variables, right?
+
+55
+00:02:07,000 --> 00:02:08,000
+So let's say my name is Navin,
+
+56
+00:02:08,000 --> 00:02:10,000
+and let's say if I'm walking on a street
+
+57
+00:02:10,000 --> 00:02:14,000
+and if somebody is asking my name, I might provide my name.
+
+58
+00:02:14,000 --> 00:02:17,000
+What if somebody is asking my email address?
+
+59
+00:02:17,000 --> 00:02:19,000
+I might provide them my email address depending
+
+60
+00:02:19,000 --> 00:02:20,000
+upon who that person is.
+
+61
+00:02:20,000 --> 00:02:25,000
+What if somebody is asking for my children's name,
+
+62
+00:02:25,000 --> 00:02:27,000
+my wife name, my family name, my Facebook password?
+
+63
+00:02:27,000 --> 00:02:30,000
+No, I'm not going to share those things,
+
+64
+00:02:30,000 --> 00:02:32,000
+it's because there's something called privacy, right?
+
+65
+00:02:32,000 --> 00:02:34,000
+And yeah, I know a lot of people don't believe in privacy,
+
+66
+00:02:34,000 --> 00:02:36,000
+but of course no one should be able
+
+67
+00:02:36,000 --> 00:02:38,000
+to get your data directly, right?
+
+68
+00:02:38,000 --> 00:02:40,000
+It's not like your data is available
+
+69
+00:02:40,000 --> 00:02:41,000
+for the entire world to see.
+
+70
+00:02:41,000 --> 00:02:43,000
+It's there, it's closed.
+
+71
+00:02:43,000 --> 00:02:44,000
+No one can see the data.
+
+72
+00:02:44,000 --> 00:02:45,000
+Of course they can see my Facebook profile,
+
+73
+00:02:45,000 --> 00:02:48,000
+but no one can see the data inside your brain.
+
+74
+00:02:48,000 --> 00:02:50,000
+That's important.
+
+75
+00:02:50,000 --> 00:02:52,000
+If they want to know your data, they have to ask
+
+76
+00:02:52,000 --> 00:02:56,000
+and you can decide do you want to share or not?
+
+77
+00:02:56,000 --> 00:02:59,000
+In the same way, let's say we have this Human class
+
+78
+00:02:59,000 --> 00:03:01,000
+and in this Human class we have a variable called "age"
+
+79
+00:03:01,000 --> 00:03:03,000
+and we have a string which is "name",
+
+80
+00:03:03,000 --> 00:03:04,000
+that's it, just two variables.
+
+81
+00:03:04,000 --> 00:03:08,000
+And now if I want to access those data, of course I have
+
+82
+00:03:08,000 --> 00:03:10,000
+to create object of Human here.
+
+83
+00:03:10,000 --> 00:03:13,000
+And let's say this is the Human object, new Human.
+
+84
+00:03:13,000 --> 00:03:16,000
+And once you got this object, with this object,
+
+85
+00:03:16,000 --> 00:03:17,000
+you can fetch data, right?
+
+86
+00:03:17,000 --> 00:03:19,000
+Of course you can set the date values as well.
+
+87
+00:03:19,000 --> 00:03:21,000
+And for this particular object,
+
+88
+00:03:21,000 --> 00:03:24,000
+I can say obj.age is, let's say 11.
+
+89
+00:03:24,000 --> 00:03:29,000
+And obj.name is, let's say Navin.
+
+90
+00:03:29,000 --> 00:03:30,000
+I know that's not my age,
+
+91
+00:03:30,000 --> 00:03:33,000
+but at this point it's okay, so we got these values
+
+92
+00:03:33,000 --> 00:03:35,000
+and we got this object created here.
+
+93
+00:03:35,000 --> 00:03:40,000
+Now what I wanna do is, what if someone ask me, "Hey Human,"
+
+94
+00:03:40,000 --> 00:03:42,000
+or maybe someone is trying to directly trying
+
+95
+00:03:42,000 --> 00:03:43,000
+to fetch the data.
+
+96
+00:03:43,000 --> 00:03:47,000
+Example, if I say S out and if I try to say obj name.
+
+97
+00:03:47,000 --> 00:03:51,000
+Now what we are doing is just by using the object,
+
+98
+00:03:51,000 --> 00:03:53,000
+anyone can fetch data, okay?
+
+99
+00:03:53,000 --> 00:03:57,000
+And this will work, okay? It'll not give any issue.
+
+100
+00:03:57,000 --> 00:03:59,000
+So I will say compile and run.
+
+101
+00:03:59,000 --> 00:04:01,000
+You can see we are able to fetch data
+
+102
+00:04:01,000 --> 00:04:04,000
+and syntactically there's no issue.
+
+103
+00:04:04,000 --> 00:04:06,000
+But then if you really think that we have
+
+104
+00:04:06,000 --> 00:04:08,000
+to implement software for the physical world
+
+105
+00:04:08,000 --> 00:04:11,000
+or the real world, it should match with the real world.
+
+106
+00:04:11,000 --> 00:04:13,000
+Not all data are directly accessible
+
+107
+00:04:13,000 --> 00:04:15,000
+and we want to control it.
+
+108
+00:04:15,000 --> 00:04:16,000
+So one way to do that is
+
+109
+00:04:16,000 --> 00:04:19,000
+what you can do is you can make your variables private.
+
+110
+00:04:19,000 --> 00:04:21,000
+Now what do you mean by this private keyword?
+
+111
+00:04:21,000 --> 00:04:23,000
+Of course we'll have a detailed discussion later.
+
+112
+00:04:23,000 --> 00:04:25,000
+At this point, private simply means,
+
+113
+00:04:25,000 --> 00:04:28,000
+this particular variable, which is age,
+
+114
+00:04:28,000 --> 00:04:31,000
+is accessible only in the same class.
+
+115
+00:04:31,000 --> 00:04:32,000
+Let me repeat:
+
+116
+00:04:32,000 --> 00:04:37,000
+This age variable is accessible in the same class.
+
+117
+00:04:37,000 --> 00:04:39,000
+The moment you make it private, it's private.
+
+118
+00:04:39,000 --> 00:04:41,000
+No one from the outside world can use it.
+
+119
+00:04:41,000 --> 00:04:44,000
+Of course I can use my data because that's private to me,
+
+120
+00:04:44,000 --> 00:04:46,000
+but you can't access my data.
+
+121
+00:04:46,000 --> 00:04:49,000
+Because that's private to me, right?
+
+122
+00:04:49,000 --> 00:04:51,000
+The same thing can be done for the variable here.
+
+123
+00:04:51,000 --> 00:04:54,000
+And if you observe the moment I do that,
+
+124
+00:04:54,000 --> 00:04:56,000
+we got an error here.
+
+125
+00:04:56,000 --> 00:04:58,000
+I mean of course vs code helps you that.
+
+126
+00:04:58,000 --> 00:05:02,000
+VS code says, "Hey, this variable age is not visible."
+
+127
+00:05:02,000 --> 00:05:05,000
+You know why it's not visible? Because it's private!
+
+128
+00:05:05,000 --> 00:05:09,000
+Now going forward, this is what you have to do.
+
+129
+00:05:09,000 --> 00:05:12,000
+Every time you create a instance variable, let me repeat.
+
+130
+00:05:12,000 --> 00:05:17,000
+Every time you create a instance variable, make it private.
+
+131
+00:05:18,000 --> 00:05:20,000
+No one from the outside world should be able to use it.
+
+132
+00:05:20,000 --> 00:05:23,000
+Now you will say, "Hey, doing that,
+
+133
+00:05:23,000 --> 00:05:26,000
+we are actually breaking all the purpose
+
+134
+00:05:26,000 --> 00:05:27,000
+of building a software," right?
+
+135
+00:05:27,000 --> 00:05:29,000
+If no one is able to access this data,
+
+136
+00:05:29,000 --> 00:05:31,000
+then why we are even creating these variables?
+
+137
+00:05:31,000 --> 00:05:32,000
+That's right.
+
+138
+00:05:32,000 --> 00:05:34,000
+The reason why we are creating this variable
+
+139
+00:05:34,000 --> 00:05:35,000
+is because we can store values
+
+140
+00:05:35,000 --> 00:05:37,000
+and someone should be able to access them.
+
+141
+00:05:37,000 --> 00:05:41,000
+They should be able to access them but not directly.
+
+142
+00:05:41,000 --> 00:05:44,000
+So there should be some indirect way.
+
+143
+00:05:44,000 --> 00:05:45,000
+Yeah, we have indirect way.
+
+144
+00:05:45,000 --> 00:05:47,000
+So the way they should be able to access this data is
+
+145
+00:05:47,000 --> 00:05:49,000
+with the help of methods.
+
+146
+00:05:49,000 --> 00:05:52,000
+Example, let's say if you want to know my name, you have
+
+147
+00:05:52,000 --> 00:05:53,000
+to ask for it
+
+148
+00:05:53,000 --> 00:05:57,000
+and I will decide should I share that data with you or not?
+
+149
+00:05:57,000 --> 00:05:58,000
+So if you say, "Hey, what's your name?"
+
+150
+00:05:58,000 --> 00:06:01,000
+I will say, okay, I will ask my brain what's my name
+
+151
+00:06:01,000 --> 00:06:03,000
+because most of the time I don't remember my own name.
+
+152
+00:06:03,000 --> 00:06:05,000
+So I will say, hey, what's my name?
+
+153
+00:06:05,000 --> 00:06:07,000
+My brain will say, "Okay, your name is Navin."
+
+154
+00:06:07,000 --> 00:06:09,000
+And then from my methods, which is my mouth
+
+155
+00:06:09,000 --> 00:06:13,000
+or by using my handwriting or by typing somewhere,
+
+156
+00:06:13,000 --> 00:06:16,000
+there's a way I have to share that data with you, right?
+
+157
+00:06:16,000 --> 00:06:20,000
+I have some methods, behavior, I can talk,
+
+158
+00:06:20,000 --> 00:06:21,000
+I can write, I can type.
+
+159
+00:06:21,000 --> 00:06:24,000
+Now using those behavior, I can share the information, okay?
+
+160
+00:06:24,000 --> 00:06:26,000
+Not like anyone can just come to me,
+
+161
+00:06:26,000 --> 00:06:29,000
+they will break my head and say, "Okay, I got the data."
+
+162
+00:06:29,000 --> 00:06:31,000
+No, that's not how it should work.
+
+163
+00:06:31,000 --> 00:06:34,000
+So how do I restrict it?
+
+164
+00:06:34,000 --> 00:06:35,000
+So what we can do is we can make it private.
+
+165
+00:06:35,000 --> 00:06:37,000
+We are restricting it.
+
+166
+00:06:37,000 --> 00:06:40,000
+The only way to access them is with the help of methods.
+
+167
+00:06:40,000 --> 00:06:42,000
+So what I can do is temporary,
+
+168
+00:06:42,000 --> 00:06:44,000
+I will just come in these two sections
+
+169
+00:06:44,000 --> 00:06:48,000
+and I will assign the value here itself and we can do that.
+
+170
+00:06:48,000 --> 00:06:49,000
+I will say name is Navin,
+
+171
+00:06:49,000 --> 00:06:53,000
+and then here coming back to public, I will say public,
+
+172
+00:06:53,000 --> 00:06:54,000
+I want to get data.
+
+173
+00:06:54,000 --> 00:06:56,000
+I want to say, "Hey, get age," okay?
+
+174
+00:06:56,000 --> 00:06:59,000
+And of course you can use any method name, doesn't matter.
+
+175
+00:06:59,000 --> 00:07:03,000
+But let's say get age and this will return a integer value.
+
+176
+00:07:03,000 --> 00:07:06,000
+So I will say int here, and this will return.
+
+177
+00:07:06,000 --> 00:07:08,000
+So this will basically return the age.
+
+178
+00:07:08,000 --> 00:07:11,000
+Another question is, can I access age here?
+
+179
+00:07:11,000 --> 00:07:13,000
+And the answer is yes you can.
+
+180
+00:07:13,000 --> 00:07:16,000
+You can access the age variable inside a method
+
+181
+00:07:16,000 --> 00:07:17,000
+of a same class.
+
+182
+00:07:17,000 --> 00:07:19,000
+That's right.
+
+183
+00:07:19,000 --> 00:07:22,000
+This getAge is defined in the same class,
+
+184
+00:07:22,000 --> 00:07:24,000
+that's why you are able to access that.
+
+185
+00:07:24,000 --> 00:07:26,000
+And if you see age here or name here,
+
+186
+00:07:26,000 --> 00:07:29,000
+so we are trying to get the data of another class,
+
+187
+00:07:29,000 --> 00:07:33,000
+demo and Human, they are two different classes.
+
+188
+00:07:33,000 --> 00:07:34,000
+Okay, makes sense now.
+
+189
+00:07:34,000 --> 00:07:36,000
+Now we can also do it for the name.
+
+190
+00:07:36,000 --> 00:07:39,000
+So for the name I will say public string getName
+
+191
+00:07:40,000 --> 00:07:44,000
+and this will basically return a name.
+
+192
+00:07:44,000 --> 00:07:48,000
+Okay? So we got two methods, get age and get name.
+
+193
+00:07:48,000 --> 00:07:50,000
+And then we are returning the age and name.
+
+194
+00:07:50,000 --> 00:07:54,000
+Now if someone wants to fetch it, I can simply say,
+
+195
+00:07:54,000 --> 00:07:56,000
+"Hey, don't call name, that will not work."
+
+196
+00:07:56,000 --> 00:07:58,000
+Because name is a variable, this is private.
+
+197
+00:07:58,000 --> 00:08:02,000
+You can access the methods, you can say obj.getName
+
+198
+00:08:02,000 --> 00:08:04,000
+That's how you can fetch a value.
+
+199
+00:08:04,000 --> 00:08:06,000
+Of course you can also fetch the age.
+
+200
+00:08:06,000 --> 00:08:09,000
+What I can do is I can just say, plus I can give a colon
+
+201
+00:08:09,000 --> 00:08:12,000
+in between and I can say obj.getAge
+
+202
+00:08:12,000 --> 00:08:13,000
+Okay?
+
+203
+00:08:13,000 --> 00:08:17,000
+Now I think we should be able to access it.
+
+204
+00:08:17,000 --> 00:08:20,000
+Let's try and compile, run.
+
+205
+00:08:20,000 --> 00:08:21,000
+Oh it's working. Can you see that?
+
+206
+00:08:21,000 --> 00:08:23,000
+We got Navin and 11.
+
+207
+00:08:23,000 --> 00:08:27,000
+So the point remember is every time you create a variable
+
+208
+00:08:27,000 --> 00:08:30,000
+which is private, we are making sure that it is restricted.
+
+209
+00:08:30,000 --> 00:08:33,000
+No one from the outside world should be able to use it.
+
+210
+00:08:33,000 --> 00:08:36,000
+So this age variable, this name variable will be used
+
+211
+00:08:36,000 --> 00:08:38,000
+by their own methods.
+
+212
+00:08:38,000 --> 00:08:40,000
+That actually makes some sense.
+
+213
+00:08:40,000 --> 00:08:43,000
+But there's one little problem here.
+
+214
+00:08:43,000 --> 00:08:44,000
+What if I want to assign the value?
+
+215
+00:08:44,000 --> 00:08:48,000
+What if I don't specify the value here? Cut and cut.
+
+216
+00:08:48,000 --> 00:08:49,000
+Let's say we have the variables,
+
+217
+00:08:49,000 --> 00:08:51,000
+but I don't assign the value.
+
+218
+00:08:51,000 --> 00:08:53,000
+Now of course, if you don't assign the value,
+
+219
+00:08:53,000 --> 00:08:56,000
+default value will be zero and a null string.
+
+220
+00:08:56,000 --> 00:08:58,000
+But how do I set the value?
+
+221
+00:08:58,000 --> 00:09:02,000
+Now for getting the data we have said get,
+
+222
+00:09:02,000 --> 00:09:04,000
+for setting data, can we say set?
+
+223
+00:09:04,000 --> 00:09:05,000
+Let's try.
+
+224
+00:09:05,000 --> 00:09:07,000
+So here for age, I will say public.
+
+225
+00:09:07,000 --> 00:09:08,000
+Now when you are setting the value,
+
+226
+00:09:08,000 --> 00:09:10,000
+you're not getting in return something, right?
+
+227
+00:09:10,000 --> 00:09:14,000
+So you will say void and you will say setAge. Okay?
+
+228
+00:09:14,000 --> 00:09:16,000
+Now it's just that when you are setting the age, you have
+
+229
+00:09:16,000 --> 00:09:19,000
+to ask, "Hey, what is a value?"
+
+230
+00:09:19,000 --> 00:09:22,000
+So maybe you can also accept a value here,
+
+231
+00:09:22,000 --> 00:09:24,000
+maybe I can say A right?
+
+232
+00:09:24,000 --> 00:09:29,000
+And then here I can say age is equal to A.
+
+233
+00:09:29,000 --> 00:09:30,000
+Now what I mean by that is
+
+234
+00:09:30,000 --> 00:09:33,000
+of course you have a method which is accepting a value,
+
+235
+00:09:33,000 --> 00:09:35,000
+assigning that to age, but how it'll work?
+
+236
+00:09:35,000 --> 00:09:37,000
+So let's come back here, which the portion
+
+237
+00:09:37,000 --> 00:09:38,000
+which we have commented,
+
+238
+00:09:38,000 --> 00:09:39,000
+I want to set the age, right?
+
+239
+00:09:39,000 --> 00:09:41,000
+So instead of setting the age to the variable,
+
+240
+00:09:41,000 --> 00:09:44,000
+I can say obj.setAge
+
+241
+00:09:44,000 --> 00:09:46,000
+We are using a method now, not the variable.
+
+242
+00:09:46,000 --> 00:09:50,000
+And in this particular bracket you can pass the argument.
+
+243
+00:09:50,000 --> 00:09:52,000
+And let's say the age is 30.
+
+244
+00:09:52,000 --> 00:09:54,000
+So now we are passing the value.
+
+245
+00:09:54,000 --> 00:09:57,000
+Now this value will be assigned to this A
+
+246
+00:09:57,000 --> 00:10:00,000
+and from A, this will be assigned to age.
+
+247
+00:10:00,000 --> 00:10:02,000
+Can we do the same thing for string?
+
+248
+00:10:02,000 --> 00:10:06,000
+Let's try, I'll say public void setName
+
+249
+00:10:06,000 --> 00:10:09,000
+And of course we have to also accept the name.
+
+250
+00:10:09,000 --> 00:10:11,000
+But what's the format of name?
+
+251
+00:10:11,000 --> 00:10:14,000
+String name I will say N this time.
+
+252
+00:10:14,000 --> 00:10:18,000
+And here I can say name is equal to N.
+
+253
+00:10:18,000 --> 00:10:21,000
+So whatever value you pass, will be assigned to this n
+
+254
+00:10:21,000 --> 00:10:24,000
+and from N it'll be assigned to name.
+
+255
+00:10:24,000 --> 00:10:26,000
+Now the same thing need to be changed here.
+
+256
+00:10:26,000 --> 00:10:28,000
+So I will just cut this part
+
+257
+00:10:28,000 --> 00:10:29,000
+and I will say cut this part as well.
+
+258
+00:10:29,000 --> 00:10:31,000
+I will say set name.
+
+259
+00:10:31,000 --> 00:10:34,000
+And in the double codes I will pass the name.
+
+260
+00:10:34,000 --> 00:10:36,000
+And the name here is Navin.
+
+261
+00:10:36,000 --> 00:10:38,000
+Or maybe I'll use a different name
+
+262
+00:10:38,000 --> 00:10:39,000
+this time I will say Reddy.
+
+263
+00:10:39,000 --> 00:10:40,000
+Okay?
+
+264
+00:10:40,000 --> 00:10:43,000
+And now I will just come back here, clear the screen,
+
+265
+00:10:43,000 --> 00:10:45,000
+compile, run.
+
+266
+00:10:45,000 --> 00:10:48,000
+Now you see that we got Reddy and 30.
+
+267
+00:10:48,000 --> 00:10:50,000
+So what we are doing is we are assigning the value
+
+268
+00:10:50,000 --> 00:10:52,000
+with the help of methods here
+
+269
+00:10:52,000 --> 00:10:56,000
+and we are getting the value with the help of methods here.
+
+270
+00:10:56,000 --> 00:10:58,000
+So that's how we can access this data.
+
+271
+00:10:58,000 --> 00:11:02,000
+Now what we are doing is we are making your variable private
+
+272
+00:11:02,000 --> 00:11:04,000
+and then the only way to access them is
+
+273
+00:11:04,000 --> 00:11:05,000
+with the help of methods, right?
+
+274
+00:11:05,000 --> 00:11:08,000
+So basically we are binding our data with the methods.
+
+275
+00:11:08,000 --> 00:11:11,000
+The only way to access that data is with methods.
+
+276
+00:11:11,000 --> 00:11:13,000
+So no one from the outside world can use
+
+277
+00:11:13,000 --> 00:11:14,000
+your variables directly.
+
+278
+00:11:14,000 --> 00:11:17,000
+So somewhere we are encapsulating the data and methods
+
+279
+00:11:17,000 --> 00:11:19,000
+and that is Encapsulation.
+
+280
+00:11:19,000 --> 00:11:21,000
+Okay? Simple stuff, right?
+
+281
+00:11:21,000 --> 00:11:24,000
+So yeah, that's it from this video.
+
+282
+00:11:24,000 --> 00:11:26,000
+Let's try to understand this more.
+
+283
+00:11:26,000 --> 00:11:28,000
+What is this get and set methods?
+
+284
+00:11:28,000 --> 00:11:30,000
+Can we use different names
+
+285
+00:11:30,000 --> 00:11:32,000
+or only this name will work?
+
+286
+00:11:32,000 --> 00:11:34,000
+That we'll discuss in the next video.
+
diff --git a/02 - Core Java/044 Source-code.url b/02 - Core Java/044 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/044 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/045 Getters and setters_en.srt b/02 - Core Java/045 Getters and setters_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..3faaa6f525133f0aa3c68fbc38d14762134e01a6
--- /dev/null
+++ b/02 - Core Java/045 Getters and setters_en.srt	
@@ -0,0 +1,328 @@
+1
+00:00:00,000 --> 00:00:02,000
+(gentle music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: Let's try to understand what these methods are
+
+3
+00:00:06,000 --> 00:00:08,000
+or can we change the name?
+
+4
+00:00:08,000 --> 00:00:11,000
+So getAge, setAge makes sense,
+
+5
+00:00:11,000 --> 00:00:13,000
+but can we use some other names?
+
+6
+00:00:13,000 --> 00:00:14,000
+Actually, we can.
+
+7
+00:00:14,000 --> 00:00:16,000
+Instead of saying getAge, we can say abc,
+
+8
+00:00:16,000 --> 00:00:18,000
+and setAge, we can say xyz.
+
+9
+00:00:18,000 --> 00:00:20,000
+We can do that, okay? There's no harm in that.
+
+10
+00:00:20,000 --> 00:00:21,000
+The only thing is when you call these methods,
+
+11
+00:00:21,000 --> 00:00:23,000
+of course you have to change the name.
+
+12
+00:00:23,000 --> 00:00:25,000
+I will say this is xyz,
+
+13
+00:00:25,000 --> 00:00:28,000
+so when you set the value, you have to call xyz,
+
+14
+00:00:28,000 --> 00:00:31,000
+and then when you fetch the value, you have to say abc,
+
+15
+00:00:31,000 --> 00:00:32,000
+and it surely works.
+
+16
+00:00:32,000 --> 00:00:36,000
+If I try to compile this and run,
+
+17
+00:00:36,000 --> 00:00:37,000
+you can see it works.
+
+18
+00:00:37,000 --> 00:00:39,000
+Now, the problem with abc and xyz or any name
+
+19
+00:00:39,000 --> 00:00:44,000
+is your method name should define what is your intention.
+
+20
+00:00:44,000 --> 00:00:46,000
+Because most of the time it's not just about writing code,
+
+21
+00:00:46,000 --> 00:00:47,000
+it's also about reading code.
+
+22
+00:00:47,000 --> 00:00:49,000
+When you write a code once,
+
+23
+00:00:49,000 --> 00:00:51,000
+it will be read by multiple people
+
+24
+00:00:51,000 --> 00:00:53,000
+in the entire lifetime of a software.
+
+25
+00:00:53,000 --> 00:00:54,000
+Why not use proper words
+
+26
+00:00:54,000 --> 00:00:56,000
+which explains what that method is doing?
+
+27
+00:00:56,000 --> 00:00:58,000
+So instead of saying abc,
+
+28
+00:00:58,000 --> 00:01:00,000
+if I say getAge,
+
+29
+00:01:00,000 --> 00:01:01,000
+it is actually makes sense, right?
+
+30
+00:01:01,000 --> 00:01:04,000
+It is much more readable what you're doing there, right?
+
+31
+00:01:04,000 --> 00:01:06,000
+And as I mentioned before,
+
+32
+00:01:06,000 --> 00:01:08,000
+it is not a compulsion to use the same name.
+
+33
+00:01:08,000 --> 00:01:12,000
+But then as a Java developer, we have adopted this standard.
+
+34
+00:01:12,000 --> 00:01:15,000
+Whenever you want to get the value of a variable,
+
+35
+00:01:15,000 --> 00:01:17,000
+the method name would be get space,
+
+36
+00:01:17,000 --> 00:01:18,000
+the other variable name,
+
+37
+00:01:18,000 --> 00:01:19,000
+the variable name, which is age.
+
+38
+00:01:19,000 --> 00:01:20,000
+To set the value,
+
+39
+00:01:20,000 --> 00:01:22,000
+you will say set and you will use the variable name,
+
+40
+00:01:22,000 --> 00:01:24,000
+which is age, okay?
+
+41
+00:01:24,000 --> 00:01:25,000
+So, that's how we can use this.
+
+42
+00:01:25,000 --> 00:01:27,000
+So, this is called a getter.
+
+43
+00:01:27,000 --> 00:01:29,000
+So for the variable user, this is a getter.
+
+44
+00:01:29,000 --> 00:01:32,000
+And when you want to set the value,
+
+45
+00:01:32,000 --> 00:01:34,000
+so the method is called setter.
+
+46
+00:01:34,000 --> 00:01:38,000
+So, we can say that those are getters and setters.
+
+47
+00:01:38,000 --> 00:01:40,000
+In fact, the beauty is
+
+48
+00:01:40,000 --> 00:01:42,000
+if I delete the entire part,
+
+49
+00:01:42,000 --> 00:01:43,000
+okay, let me just do that.
+
+50
+00:01:43,000 --> 00:01:46,000
+I know we need to type that once again.
+
+51
+00:01:46,000 --> 00:01:47,000
+Actually, you don't.
+
+52
+00:01:47,000 --> 00:01:49,000
+Most of the IDEs have this amazing feature.
+
+53
+00:01:49,000 --> 00:01:52,000
+You can just right-click and there's a option of source.
+
+54
+00:01:52,000 --> 00:01:55,000
+In fact, it doesn't matter which IDE you're using,
+
+55
+00:01:55,000 --> 00:01:56,000
+you will see the option of source
+
+56
+00:01:56,000 --> 00:01:58,000
+or insert code, something like this.
+
+57
+00:01:58,000 --> 00:02:01,000
+So it will say Source Action, what do you want?
+
+58
+00:02:01,000 --> 00:02:03,000
+You want to get,
+
+59
+00:02:03,000 --> 00:02:07,000
+you have to say Generate Getters and Setters for me.
+
+60
+00:02:07,000 --> 00:02:08,000
+Click on that.
+
+61
+00:02:08,000 --> 00:02:09,000
+For both the variables,
+
+62
+00:02:09,000 --> 00:02:11,000
+and click on OK.
+
+63
+00:02:11,000 --> 00:02:14,000
+You can see it will generate the methods for you
+
+64
+00:02:14,000 --> 00:02:16,000
+and you see that variable names, it's same.
+
+65
+00:02:16,000 --> 00:02:21,000
+getAge, setAge, and then we got getName, setName, okay?
+
+66
+00:02:21,000 --> 00:02:23,000
+And those are called getters and setters.
+
+67
+00:02:23,000 --> 00:02:25,000
+And of course, there is no compulsion
+
+68
+00:02:25,000 --> 00:02:26,000
+to have both the methods.
+
+69
+00:02:26,000 --> 00:02:28,000
+You can only have getName.
+
+70
+00:02:28,000 --> 00:02:30,000
+You don't want to have setName, that's your choice.
+
+71
+00:02:30,000 --> 00:02:32,000
+There's no compulsion that there should be both.
+
+72
+00:02:32,000 --> 00:02:34,000
+It depends upon you how you want to implement it.
+
+73
+00:02:34,000 --> 00:02:38,000
+For this example, I want to assign value to age and name.
+
+74
+00:02:38,000 --> 00:02:39,000
+I want to get the values as well
+
+75
+00:02:39,000 --> 00:02:41,000
+and that's why I'm using this tool.
+
+76
+00:02:41,000 --> 00:02:42,000
+So only thing is for every variable,
+
+77
+00:02:42,000 --> 00:02:45,000
+you need two methods, getters and setters, okay?
+
+78
+00:02:45,000 --> 00:02:46,000
+So yeah, that's it.
+
+79
+00:02:46,000 --> 00:02:48,000
+But there's only one issue now.
+
+80
+00:02:48,000 --> 00:02:50,000
+If I use the code which is given by the IDE,
+
+81
+00:02:50,000 --> 00:02:53,000
+you can see this new keyword here, we got this.
+
+82
+00:02:53,000 --> 00:02:56,000
+What is this? So, let's talk about this in the next video.
+
diff --git a/02 - Core Java/045 Source-code.url b/02 - Core Java/045 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/045 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/046 Source-code.url b/02 - Core Java/046 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/046 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/046 This keyword_en.srt b/02 - Core Java/046 This keyword_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..0a887ee8c08a78f605da5ffe7c78ecbc4cc0e4f1
--- /dev/null
+++ b/02 - Core Java/046 This keyword_en.srt	
@@ -0,0 +1,908 @@
+1
+00:00:00,000 --> 00:00:03,000
+(calm piano music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, let's talk about this
+
+3
+00:00:06,000 --> 00:00:07,000
+because in the previous video,
+
+4
+00:00:07,000 --> 00:00:08,000
+we were doing something
+
+5
+00:00:08,000 --> 00:00:10,000
+and then suddenly we got this keyword.
+
+6
+00:00:10,000 --> 00:00:13,000
+So it's important now to talk about this keyword here.
+
+7
+00:00:13,000 --> 00:00:15,000
+Now, what I will do is I will just remove this,
+
+8
+00:00:15,000 --> 00:00:19,000
+or I will just change this variable name back to A and N.
+
+9
+00:00:19,000 --> 00:00:24,000
+And of course, here, we have to say A and N, right?
+
+10
+00:00:24,000 --> 00:00:26,000
+And let me remove this keyword from here
+
+11
+00:00:26,000 --> 00:00:27,000
+just to see if this works.
+
+12
+00:00:27,000 --> 00:00:29,000
+Now, if I remove this keyword from there
+
+13
+00:00:29,000 --> 00:00:31,000
+and you find on this code compile, okay,
+
+14
+00:00:31,000 --> 00:00:34,000
+there is some problem with the variable names.
+
+15
+00:00:34,000 --> 00:00:36,000
+I think we are still calling X, Y, Z,
+
+16
+00:00:36,000 --> 00:00:37,000
+so it should be setAge.
+
+17
+00:00:38,000 --> 00:00:39,000
+And we are still calling A, B, C.
+
+18
+00:00:39,000 --> 00:00:42,000
+It should be getAge, the same thing
+
+19
+00:00:42,000 --> 00:00:44,000
+which we have done in the previous video.
+
+20
+00:00:44,000 --> 00:00:47,000
+Okay, so if I save this and if I go back and compile,
+
+21
+00:00:47,000 --> 00:00:51,000
+so compile, done, running, done,
+
+22
+00:00:51,000 --> 00:00:54,000
+so you can see we got the values right?
+
+23
+00:00:54,000 --> 00:00:56,000
+Now, the thing is when you talk about this variable like age
+
+24
+00:00:56,000 --> 00:00:58,000
+and when you are passing a here,
+
+25
+00:00:58,000 --> 00:01:00,000
+we are using two different variables right?
+
+26
+00:01:00,000 --> 00:01:04,000
+Now, the point to remember here is this a variable here
+
+27
+00:01:04,000 --> 00:01:05,000
+is a local variable.
+
+28
+00:01:05,000 --> 00:01:09,000
+This age variable here is a instance variable, right?
+
+29
+00:01:09,000 --> 00:01:11,000
+If you want to understand that with a diagram,
+
+30
+00:01:11,000 --> 00:01:13,000
+you can just go back here.
+
+31
+00:01:13,000 --> 00:01:15,000
+We have a stack memory, remember?
+
+32
+00:01:15,000 --> 00:01:17,000
+We have talked about stack and heap.
+
+33
+00:01:17,000 --> 00:01:19,000
+So we got a stack here and then we got heap here.
+
+34
+00:01:19,000 --> 00:01:22,000
+Now, the moment you create the human object,
+
+35
+00:01:22,000 --> 00:01:23,000
+we got this object here, Human.
+
+36
+00:01:23,000 --> 00:01:25,000
+So in this, we have a Human object
+
+37
+00:01:25,000 --> 00:01:29,000
+and of course, it will have some address, let's say, 101.
+
+38
+00:01:29,000 --> 00:01:32,000
+So we got obj and the address is 101.
+
+39
+00:01:32,000 --> 00:01:33,000
+That's the first object we got.
+
+40
+00:01:33,000 --> 00:01:37,000
+And there's a link here which we cannot ignore.
+
+41
+00:01:37,000 --> 00:01:39,000
+And then we have some more variables.
+
+42
+00:01:39,000 --> 00:01:41,000
+You can see if you execute.
+
+43
+00:01:41,000 --> 00:01:44,000
+And of course, this was my main stack.
+
+44
+00:01:45,000 --> 00:01:47,000
+Now, we are executing which method?
+
+45
+00:01:47,000 --> 00:01:52,000
+So if you say setAge, we are executing setAge method, right?
+
+46
+00:01:52,000 --> 00:01:54,000
+Now, setAge will have its own stack here.
+
+47
+00:01:54,000 --> 00:01:56,000
+Let's say, we have a setAge stack here.
+
+48
+00:01:56,000 --> 00:01:57,000
+You know what?
+
+49
+00:01:57,000 --> 00:01:59,000
+I just have to zoom it a bit
+
+50
+00:01:59,000 --> 00:02:01,000
+and here, let me create segments.
+
+51
+00:02:01,000 --> 00:02:04,000
+So we got multiple segments here
+
+52
+00:02:04,000 --> 00:02:05,000
+and of course, this will be linked
+
+53
+00:02:05,000 --> 00:02:08,000
+with this particular variable here.
+
+54
+00:02:08,000 --> 00:02:10,000
+And don't you think this box
+
+55
+00:02:10,000 --> 00:02:12,000
+which is address 101 is an object of Human?
+
+56
+00:02:12,000 --> 00:02:14,000
+So it will also have the instance variable.
+
+57
+00:02:14,000 --> 00:02:15,000
+How many instance variable we have.
+
+58
+00:02:15,000 --> 00:02:20,000
+We have age and name. So we got age and we got name here.
+
+59
+00:02:20,000 --> 00:02:23,000
+Now, if you look at the setAge, now setAge,
+
+60
+00:02:23,000 --> 00:02:27,000
+this particular stack is of setAge.
+
+61
+00:02:27,000 --> 00:02:28,000
+Every method will have its own stack.
+
+62
+00:02:28,000 --> 00:02:31,000
+And in this, we got a variable called a,
+
+63
+00:02:31,000 --> 00:02:34,000
+and the value for a which we are passing is study.
+
+64
+00:02:34,000 --> 00:02:36,000
+So we got 30 here, okay?
+
+65
+00:02:36,000 --> 00:02:40,000
+And then the same value 30, we are assigning to age.
+
+66
+00:02:40,000 --> 00:02:43,000
+That means we are changing this variable,
+
+67
+00:02:43,000 --> 00:02:45,000
+and we are assigning a value which is 30 there,
+
+68
+00:02:45,000 --> 00:02:47,000
+if that makes sense, okay?
+
+69
+00:02:47,000 --> 00:02:50,000
+So both the value for a and age is 30.
+
+70
+00:02:50,000 --> 00:02:52,000
+And that's why when you fetch data,
+
+71
+00:02:52,000 --> 00:02:56,000
+when you say getAge, it will return the value of age
+
+72
+00:02:56,000 --> 00:02:59,000
+in the object which is 30, in this case.
+
+73
+00:02:59,000 --> 00:03:00,000
+And that is perfectly working.
+
+74
+00:03:00,000 --> 00:03:03,000
+Now, the problem is what if I just make
+
+75
+00:03:03,000 --> 00:03:08,000
+this particular variable age as age, I mean, a as age?
+
+76
+00:03:08,000 --> 00:03:10,000
+Now, what I want is I want my local variable
+
+77
+00:03:10,000 --> 00:03:13,000
+and my instance variable both
+
+78
+00:03:13,000 --> 00:03:16,000
+to have the same variable name.
+
+79
+00:03:16,000 --> 00:03:19,000
+What do you mean by that is if I remove this a from here,
+
+80
+00:03:19,000 --> 00:03:22,000
+the variable name here will be age.
+
+81
+00:03:22,000 --> 00:03:25,000
+So both the variable name, the local variable
+
+82
+00:03:25,000 --> 00:03:28,000
+and the instance variable have the same name,
+
+83
+00:03:28,000 --> 00:03:30,000
+then it should work, right?
+
+84
+00:03:30,000 --> 00:03:31,000
+What we're trying to do is
+
+85
+00:03:31,000 --> 00:03:33,000
+the age variable will get 30 here.
+
+86
+00:03:33,000 --> 00:03:37,000
+So of course, in this stack, we got 30.
+
+87
+00:03:37,000 --> 00:03:40,000
+And if you see we are assigning age is equal to age.
+
+88
+00:03:40,000 --> 00:03:42,000
+So I'm expecting that this age will get the value
+
+89
+00:03:42,000 --> 00:03:45,000
+from this particular age. It should work, right?
+
+90
+00:03:45,000 --> 00:03:46,000
+Let's try.
+
+91
+00:03:46,000 --> 00:03:51,000
+If I go back to my code and compile and run,
+
+92
+00:03:51,000 --> 00:03:52,000
+oh, can you see that?
+
+93
+00:03:52,000 --> 00:03:54,000
+The value for age is still zero.
+
+94
+00:03:54,000 --> 00:03:56,000
+That means the assignment which we are assuming
+
+95
+00:03:56,000 --> 00:03:58,000
+that it will be 30, it is still zero.
+
+96
+00:03:58,000 --> 00:04:03,000
+Why? The reason is if we look at line number 11,
+
+97
+00:04:03,000 --> 00:04:07,000
+and if you see it, we are saying age is equal to age.
+
+98
+00:04:07,000 --> 00:04:10,000
+The problem is by default, now see,
+
+99
+00:04:10,000 --> 00:04:12,000
+this age can be local variable.
+
+100
+00:04:12,000 --> 00:04:14,000
+This age can be instance variable, right?
+
+101
+00:04:14,000 --> 00:04:17,000
+Because the names are same. So can we do this?
+
+102
+00:04:17,000 --> 00:04:21,000
+Can we say it is possible that
+
+103
+00:04:21,000 --> 00:04:24,000
+the age here is actually a local variable?
+
+104
+00:04:24,000 --> 00:04:26,000
+It is also possible that
+
+105
+00:04:26,000 --> 00:04:29,000
+the age is assigning value to itself.
+
+106
+00:04:29,000 --> 00:04:32,000
+Maybe this age is not even a instance variable.
+
+107
+00:04:32,000 --> 00:04:35,000
+That means this age is assigning value to itself
+
+108
+00:04:35,000 --> 00:04:39,000
+and this age here, which we have created,
+
+109
+00:04:39,000 --> 00:04:41,000
+it is still zero.
+
+110
+00:04:41,000 --> 00:04:42,000
+And that's why we are getting zero.
+
+111
+00:04:42,000 --> 00:04:44,000
+How do we solve this problem?
+
+112
+00:04:44,000 --> 00:04:46,000
+So somewhere we have to mention, hey, you know?
+
+113
+00:04:46,000 --> 00:04:48,000
+This particular age here, this is not a local variable.
+
+114
+00:04:48,000 --> 00:04:49,000
+This is an instance variable.
+
+115
+00:04:49,000 --> 00:04:52,000
+So remember this point, the preference will always give,
+
+116
+00:04:52,000 --> 00:04:54,000
+always be given to local variable.
+
+117
+00:04:54,000 --> 00:04:58,000
+So in case of confusion, it is always the local variable.
+
+118
+00:04:58,000 --> 00:04:59,000
+We have to mention by some way,
+
+119
+00:04:59,000 --> 00:05:01,000
+hey, this is not local variable.
+
+120
+00:05:01,000 --> 00:05:03,000
+That's an instance variable. How do you mention that?
+
+121
+00:05:03,000 --> 00:05:05,000
+So in order to say that's an instance variable,
+
+122
+00:05:05,000 --> 00:05:06,000
+can we do this?
+
+123
+00:05:06,000 --> 00:05:08,000
+Can we say Human?
+
+124
+00:05:08,000 --> 00:05:11,000
+Can we create object here itself, obj1 = new Human?
+
+125
+00:05:11,000 --> 00:05:14,000
+And then we can say obj1.age.
+
+126
+00:05:14,000 --> 00:05:16,000
+Now, what we are doing is we are saying
+
+127
+00:05:16,000 --> 00:05:19,000
+this age is a instance variable.
+
+128
+00:05:19,000 --> 00:05:20,000
+And you might be thinking,
+
+129
+00:05:20,000 --> 00:05:24,000
+hey, how can we use age with a object?
+
+130
+00:05:24,000 --> 00:05:24,000
+See, we can't do that
+
+131
+00:05:24,000 --> 00:05:27,000
+because we are in the same class, okay?
+
+132
+00:05:27,000 --> 00:05:28,000
+We were not able to do that here
+
+133
+00:05:28,000 --> 00:05:30,000
+because we were in different class.
+
+134
+00:05:30,000 --> 00:05:33,000
+But again, the problem is we are saying this age is instance
+
+135
+00:05:33,000 --> 00:05:35,000
+and this age is local, this should work.
+
+136
+00:05:35,000 --> 00:05:36,000
+Let's see if this is a problem
+
+137
+00:05:36,000 --> 00:05:38,000
+or we have solved the problem.
+
+138
+00:05:38,000 --> 00:05:42,000
+Let's run this. Oh, it is still zero. What is happening?
+
+139
+00:05:42,000 --> 00:05:44,000
+Let's try to understand more.
+
+140
+00:05:44,000 --> 00:05:46,000
+Now, when you execute this setAge method,
+
+141
+00:05:46,000 --> 00:05:49,000
+what we are doing is we are creating a new object.
+
+142
+00:05:49,000 --> 00:05:50,000
+Oh, that's the issue.
+
+143
+00:05:50,000 --> 00:05:54,000
+We are basically creating a new object.
+
+144
+00:05:54,000 --> 00:05:57,000
+Okay, how do we solve this problem?
+
+145
+00:05:57,000 --> 00:05:58,000
+We don't want to get new object
+
+146
+00:05:58,000 --> 00:06:00,000
+because the moment you create new object,
+
+147
+00:06:00,000 --> 00:06:02,000
+what will happen here is it will create a new object,
+
+148
+00:06:02,000 --> 00:06:04,000
+let's say 103.
+
+149
+00:06:04,000 --> 00:06:05,000
+And this will have,
+
+150
+00:06:05,000 --> 00:06:08,000
+this will also have age equal to name equal to,
+
+151
+00:06:08,000 --> 00:06:10,000
+and what value you're assigning here?
+
+152
+00:06:10,000 --> 00:06:11,000
+You're assigning value which is 30.
+
+153
+00:06:11,000 --> 00:06:16,000
+And then here in this setAge, you will create obj1
+
+154
+00:06:17,000 --> 00:06:20,000
+which will have the address 103 and there's a link here.
+
+155
+00:06:20,000 --> 00:06:22,000
+So the value which you are changing is
+
+156
+00:06:22,000 --> 00:06:25,000
+of this age, not this one.
+
+157
+00:06:25,000 --> 00:06:28,000
+We want to assign the value to this particular age.
+
+158
+00:06:28,000 --> 00:06:31,000
+That means creating a new object is not a good idea.
+
+159
+00:06:31,000 --> 00:06:34,000
+Okay, how do I clear this? Let's remove this.
+
+160
+00:06:34,000 --> 00:06:35,000
+In fact, you know? this is a problem.
+
+161
+00:06:35,000 --> 00:06:37,000
+This is creating a new object.
+
+162
+00:06:37,000 --> 00:06:39,000
+Okay, if I don't want to get a new object,
+
+163
+00:06:39,000 --> 00:06:42,000
+how do I access this obj?
+
+164
+00:06:42,000 --> 00:06:44,000
+Oh, I got an idea here.
+
+165
+00:06:44,000 --> 00:06:49,000
+What if with this 30, if I can pass the object itself,
+
+166
+00:06:49,000 --> 00:06:50,000
+can we, will it solve the problem?
+
+167
+00:06:50,000 --> 00:06:54,000
+With 30, if you can pass this particular object,
+
+168
+00:06:54,000 --> 00:06:58,000
+and we can accept the object here.
+
+169
+00:06:58,000 --> 00:07:02,000
+What type of object it is? It is human, Human obj.
+
+170
+00:07:02,000 --> 00:07:05,000
+And then here, we can simply assign the value.
+
+171
+00:07:05,000 --> 00:07:08,000
+So what I'm doing is if you observe correctly,
+
+172
+00:07:08,000 --> 00:07:10,000
+we are not creating a new object.
+
+173
+00:07:10,000 --> 00:07:14,000
+We are basically passing the reference of the old object.
+
+174
+00:07:14,000 --> 00:07:19,000
+So here, it will be not 103, it will be 101, okay?
+
+175
+00:07:21,000 --> 00:07:24,000
+So this obj1 here will get the address 101,
+
+176
+00:07:24,000 --> 00:07:27,000
+and we can simply say obj1.age.
+
+177
+00:07:27,000 --> 00:07:29,000
+And now, we are not referring to this address,
+
+178
+00:07:29,000 --> 00:07:31,000
+we are referring to this address.
+
+179
+00:07:31,000 --> 00:07:33,000
+So we can change the age value 30,
+
+180
+00:07:33,000 --> 00:07:35,000
+and let's see if this works.
+
+181
+00:07:35,000 --> 00:07:36,000
+I hope this will work.
+
+182
+00:07:36,000 --> 00:07:40,000
+Compile, sorry, compile, run.
+
+183
+00:07:40,000 --> 00:07:43,000
+Oh, it is working. It is working.
+
+184
+00:07:43,000 --> 00:07:44,000
+So basically, the important thing
+
+185
+00:07:44,000 --> 00:07:45,000
+is how do you differentiate
+
+186
+00:07:45,000 --> 00:07:48,000
+between instance variable and a local variable?
+
+187
+00:07:48,000 --> 00:07:51,000
+It's bypassing the object itself,
+
+188
+00:07:51,000 --> 00:07:54,000
+but there's one little problem here.
+
+189
+00:07:54,000 --> 00:07:59,000
+The problem is if you read this line, it says obj.setAge
+
+190
+00:07:59,000 --> 00:08:02,000
+and then you're passing the obj object as well.
+
+191
+00:08:02,000 --> 00:08:03,000
+Why we have to do this?
+
+192
+00:08:03,000 --> 00:08:08,000
+Why you have to mention obj two times. Now, Java knows this.
+
+193
+00:08:08,000 --> 00:08:10,000
+Java says, hey, you don't worry.
+
+194
+00:08:10,000 --> 00:08:11,000
+Why you have to pass the object two times?
+
+195
+00:08:11,000 --> 00:08:14,000
+I mean, you're calling the method by using the object.
+
+196
+00:08:14,000 --> 00:08:15,000
+You are also passing the object.
+
+197
+00:08:15,000 --> 00:08:18,000
+Don't do that. Don't pass the object.
+
+198
+00:08:18,000 --> 00:08:20,000
+By default, I will give you this obj.
+
+199
+00:08:20,000 --> 00:08:22,000
+You don't even have to accept this obj.
+
+200
+00:08:22,000 --> 00:08:25,000
+What if Java says, hey don't worry.
+
+201
+00:08:25,000 --> 00:08:27,000
+Don't create the object, don't pass the object.
+
+202
+00:08:27,000 --> 00:08:30,000
+I will give you the object and that object, my friend,
+
+203
+00:08:30,000 --> 00:08:33,000
+in fact, you know, when we had Human here,
+
+204
+00:08:33,000 --> 00:08:35,000
+we don't even need this Human line here.
+
+205
+00:08:35,000 --> 00:08:38,000
+We could have removed that and even obj would've worked.
+
+206
+00:08:38,000 --> 00:08:41,000
+So your Java says, hey, why do you even use this obj
+
+207
+00:08:41,000 --> 00:08:43,000
+when we can simply use this?
+
+208
+00:08:43,000 --> 00:08:48,000
+Now, this is a keyword which represents the current object.
+
+209
+00:08:48,000 --> 00:08:50,000
+Now, when I say current object, what it means?
+
+210
+00:08:50,000 --> 00:08:53,000
+The object which is calling the method.
+
+211
+00:08:53,000 --> 00:08:56,000
+SetAge is called OBJ, which is this object.
+
+212
+00:08:57,000 --> 00:09:00,000
+Here in this method, we can actually use that object
+
+213
+00:09:00,000 --> 00:09:02,000
+with the help of this keyword.
+
+214
+00:09:02,000 --> 00:09:04,000
+So this refers to the current object
+
+215
+00:09:04,000 --> 00:09:06,000
+who is calling the setAge.
+
+216
+00:09:06,000 --> 00:09:08,000
+I hope that makes sense.
+
+217
+00:09:08,000 --> 00:09:10,000
+So from this point, we are always
+
+218
+00:09:10,000 --> 00:09:13,000
+going to use this which represent the current object, okay?
+
+219
+00:09:13,000 --> 00:09:18,000
+So here as well, instead of using name or n,
+
+220
+00:09:18,000 --> 00:09:20,000
+I should have used name.
+
+221
+00:09:20,000 --> 00:09:21,000
+The only thing is we have to refer
+
+222
+00:09:21,000 --> 00:09:24,000
+the part, first name here is this.name,
+
+223
+00:09:24,000 --> 00:09:26,000
+which is the object itself.
+
+224
+00:09:26,000 --> 00:09:27,000
+The current object.
+
+225
+00:09:27,000 --> 00:09:30,000
+I hope this all this thing have made sense.
+
+226
+00:09:30,000 --> 00:09:32,000
+This is what this keyword is.
+
+227
+00:09:32,000 --> 00:09:34,000
+And yeah, that's it from this video.
+
diff --git a/02 - Core Java/047 Constructor_en.srt b/02 - Core Java/047 Constructor_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..bb8edd0636169e7b881aad85e1b80e7357552a5d
--- /dev/null
+++ b/02 - Core Java/047 Constructor_en.srt	
@@ -0,0 +1,736 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle piano music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, we'll talk about constructors.
+
+3
+00:00:06,000 --> 00:00:07,000
+Now what are constructors?
+
+4
+00:00:07,000 --> 00:00:09,000
+Now look at this example here, which is of human.
+
+5
+00:00:09,000 --> 00:00:10,000
+Now when you talk about human,
+
+6
+00:00:10,000 --> 00:00:11,000
+we have some variables, right?
+
+7
+00:00:11,000 --> 00:00:13,000
+Of course, when you talk about this two variables,
+
+8
+00:00:13,000 --> 00:00:15,000
+these are instance variable,
+
+9
+00:00:15,000 --> 00:00:18,000
+and then we have seen in the image as well.
+
+10
+00:00:18,000 --> 00:00:20,000
+Basically when you create an object example in this,
+
+11
+00:00:20,000 --> 00:00:23,000
+we are just creating one object,
+
+12
+00:00:23,000 --> 00:00:26,000
+and that object is getting created inside the heap memory.
+
+13
+00:00:26,000 --> 00:00:28,000
+You can see this is the object we got.
+
+14
+00:00:28,000 --> 00:00:29,000
+And of course with that object we have assigned
+
+15
+00:00:29,000 --> 00:00:31,000
+the value for the age,
+
+16
+00:00:31,000 --> 00:00:32,000
+we have assigned the value for the name as well,
+
+17
+00:00:32,000 --> 00:00:35,000
+which is ready. But I'm not return it here,
+
+18
+00:00:35,000 --> 00:00:38,000
+but we know that the object is created.
+
+19
+00:00:38,000 --> 00:00:41,000
+Now the thing is, when you create the object,
+
+20
+00:00:41,000 --> 00:00:43,000
+if you observe the line number 29,
+
+21
+00:00:43,000 --> 00:00:46,000
+on this line, when you create the object, what happens?
+
+22
+00:00:46,000 --> 00:00:48,000
+When you create the object in the heap memory,
+
+23
+00:00:48,000 --> 00:00:50,000
+it will just create a blank object.
+
+24
+00:00:50,000 --> 00:00:54,000
+Example. If I try to remove this, if I keep it empty,
+
+25
+00:00:54,000 --> 00:00:57,000
+it will create a object with a value.
+
+26
+00:00:57,000 --> 00:00:58,000
+So the value would be,
+
+27
+00:00:58,000 --> 00:01:01,000
+I mean it will have a variable which is age,
+
+28
+00:01:01,000 --> 00:01:02,000
+and the value will be zero,
+
+29
+00:01:02,000 --> 00:01:05,000
+and it will have a variable called a name,
+
+30
+00:01:05,000 --> 00:01:07,000
+and the value will be null, right?
+
+31
+00:01:07,000 --> 00:01:10,000
+I will just try to print those things.
+
+32
+00:01:10,000 --> 00:01:13,000
+What if I do is, I will just print the same statement
+
+33
+00:01:13,000 --> 00:01:15,000
+before assigning the value, right?
+
+34
+00:01:15,000 --> 00:01:18,000
+So I'm printing it here and I will command this section.
+
+35
+00:01:18,000 --> 00:01:19,000
+So that's how you command, right?
+
+36
+00:01:19,000 --> 00:01:21,000
+I don't want this time to be executed.
+
+37
+00:01:21,000 --> 00:01:24,000
+And now if I go back here and
+
+38
+00:01:24,000 --> 00:01:25,000
+compile
+
+39
+00:01:25,000 --> 00:01:27,000
+and run, you can see we got null.
+
+40
+00:01:27,000 --> 00:01:30,000
+Null basically is when you don't have the data assigned
+
+41
+00:01:30,000 --> 00:01:31,000
+to object type.
+
+42
+00:01:31,000 --> 00:01:34,000
+That's right. String is an object type.
+
+43
+00:01:34,000 --> 00:01:36,000
+We'll discuss about string later in detail.
+
+44
+00:01:36,000 --> 00:01:38,000
+As of now, just remember by default
+
+45
+00:01:38,000 --> 00:01:40,000
+the value for string is null,
+
+46
+00:01:40,000 --> 00:01:42,000
+and the default value for integer is zero.
+
+47
+00:01:42,000 --> 00:01:46,000
+Okay, that means if you don't assign this values,
+
+48
+00:01:46,000 --> 00:01:48,000
+there will be default values.
+
+49
+00:01:48,000 --> 00:01:49,000
+What I want here is,
+
+50
+00:01:49,000 --> 00:01:52,000
+of course there is a way you can assign the values later.
+
+51
+00:01:52,000 --> 00:01:54,000
+But what if I want to assign the value
+
+52
+00:01:54,000 --> 00:01:57,000
+when the object is created?
+
+53
+00:01:57,000 --> 00:01:59,000
+That's right, on this line itself,
+
+54
+00:01:59,000 --> 00:02:00,000
+I want to assign the value.
+
+55
+00:02:00,000 --> 00:02:02,000
+That means the moment I get the object,
+
+56
+00:02:02,000 --> 00:02:03,000
+I don't want to have a null value,
+
+57
+00:02:03,000 --> 00:02:05,000
+I want to have some default values.
+
+58
+00:02:05,000 --> 00:02:08,000
+Example, let's say by default every object created,
+
+59
+00:02:08,000 --> 00:02:09,000
+the name should be something else.
+
+60
+00:02:09,000 --> 00:02:12,000
+The name should be, let's say Babu or something else.
+
+61
+00:02:12,000 --> 00:02:14,000
+I'm not sure, but can we have a default name?
+
+62
+00:02:14,000 --> 00:02:16,000
+Can we have a default age?
+
+63
+00:02:16,000 --> 00:02:18,000
+So let's say for my application,
+
+64
+00:02:18,000 --> 00:02:20,000
+this application can be used only by those people
+
+65
+00:02:20,000 --> 00:02:23,000
+who are 12 and about.
+
+66
+00:02:23,000 --> 00:02:25,000
+So I can simply say, hey, the minimum age for this is 12.
+
+67
+00:02:25,000 --> 00:02:28,000
+So by default the value for the age should be 12.
+
+68
+00:02:28,000 --> 00:02:29,000
+Can we do that?
+
+69
+00:02:30,000 --> 00:02:32,000
+So how do we achieve that?
+
+70
+00:02:32,000 --> 00:02:34,000
+Of course, we can assign the values here,
+
+71
+00:02:34,000 --> 00:02:37,000
+or we can use something called a constructor.
+
+72
+00:02:37,000 --> 00:02:39,000
+Now how a constructor looks like,
+
+73
+00:02:39,000 --> 00:02:43,000
+so a constructor looks like a method itself.
+
+74
+00:02:43,000 --> 00:02:46,000
+Let me repeat. A constructor looks like a method itself.
+
+75
+00:02:46,000 --> 00:02:48,000
+That means a constructor will have a name,
+
+76
+00:02:48,000 --> 00:02:50,000
+a constructor will have the round brackets.
+
+77
+00:02:50,000 --> 00:02:53,000
+Example, if we talk about methods here we have a name
+
+78
+00:02:53,000 --> 00:02:56,000
+and we have a round bracket in the same way
+
+79
+00:02:56,000 --> 00:02:59,000
+for the constructor as well, we have to use that.
+
+80
+00:02:59,000 --> 00:03:01,000
+So what I will do is I will say public.
+
+81
+00:03:01,000 --> 00:03:03,000
+Now the only changes in the constructor,
+
+82
+00:03:03,000 --> 00:03:06,000
+you don't specify the written type.
+
+83
+00:03:06,000 --> 00:03:09,000
+Okay? So we can directly mention the constructor name here,
+
+84
+00:03:09,000 --> 00:03:12,000
+but what should be my constructor name?
+
+85
+00:03:12,000 --> 00:03:15,000
+Now there's a compulsion that your constructor name
+
+86
+00:03:15,000 --> 00:03:17,000
+should be same as your class name.
+
+87
+00:03:17,000 --> 00:03:19,000
+So what is my class name? It's human.
+
+88
+00:03:19,000 --> 00:03:20,000
+And then since it looks like a method,
+
+89
+00:03:20,000 --> 00:03:23,000
+we can give a round bracket and we can open and close
+
+90
+00:03:23,000 --> 00:03:24,000
+the curly brackets.
+
+91
+00:03:24,000 --> 00:03:27,000
+Now one thing I wanted to mention, you can see
+
+92
+00:03:27,000 --> 00:03:29,000
+with the curly packets are mentioned just I mean,
+
+93
+00:03:29,000 --> 00:03:31,000
+for the opening brackets are just
+
+94
+00:03:31,000 --> 00:03:32,000
+mentioned on the same line.
+
+95
+00:03:32,000 --> 00:03:35,000
+And here the curly brackets are mentioned on the new line,
+
+96
+00:03:35,000 --> 00:03:36,000
+both works.
+
+97
+00:03:36,000 --> 00:03:38,000
+Some people prefer to use on the same line,
+
+98
+00:03:38,000 --> 00:03:40,000
+some people prefer to use on next line.
+
+99
+00:03:40,000 --> 00:03:41,000
+So anything works.
+
+100
+00:03:41,000 --> 00:03:44,000
+Now in this constructor I can assign the values,
+
+101
+00:03:44,000 --> 00:03:46,000
+but at this point let's not assign the value,
+
+102
+00:03:46,000 --> 00:03:49,000
+I will just simply print the statement.
+
+103
+00:03:49,000 --> 00:03:54,000
+I will say is sout, and here I will print in constructor.
+
+104
+00:03:54,000 --> 00:03:56,000
+So you can see we are printing in constructor here.
+
+105
+00:03:56,000 --> 00:03:59,000
+So that's our constructor.
+
+106
+00:03:59,000 --> 00:04:00,000
+Okay, so let me repeat what is constructor?
+
+107
+00:04:00,000 --> 00:04:03,000
+So constructor is a special method, that's right,
+
+108
+00:04:03,000 --> 00:04:05,000
+because it looks like a method.
+
+109
+00:04:05,000 --> 00:04:06,000
+It has the same name as a class name.
+
+110
+00:04:06,000 --> 00:04:08,000
+So those are the rules you have to remember.
+
+111
+00:04:08,000 --> 00:04:11,000
+The constructor will have the same name as a class name.
+
+112
+00:04:11,000 --> 00:04:13,000
+A constructor never returns anything.
+
+113
+00:04:13,000 --> 00:04:15,000
+You don't have to mention int, float,
+
+114
+00:04:15,000 --> 00:04:16,000
+or string anything there.
+
+115
+00:04:16,000 --> 00:04:18,000
+So just specify the access, which is public,
+
+116
+00:04:18,000 --> 00:04:21,000
+and then mention the name, which is human.
+
+117
+00:04:21,000 --> 00:04:23,000
+And in this you can do whatever you want.
+
+118
+00:04:23,000 --> 00:04:26,000
+Okay, so I'm just printing in constructor.
+
+119
+00:04:26,000 --> 00:04:28,000
+So let me just try and compile.
+
+120
+00:04:28,000 --> 00:04:30,000
+So compilation done. There's no problem.
+
+121
+00:04:30,000 --> 00:04:34,000
+When I done this code, one thing to observe, nowhere,
+
+122
+00:04:34,000 --> 00:04:36,000
+see, when you talk about these methods like get age
+
+123
+00:04:36,000 --> 00:04:39,000
+or set age, all these methods we have called them, right?
+
+124
+00:04:39,000 --> 00:04:41,000
+So this is where you are calling them.
+
+125
+00:04:41,000 --> 00:04:44,000
+Constructor, you can see we are not calling it,
+
+126
+00:04:44,000 --> 00:04:48,000
+but still constructor will be called.
+
+127
+00:04:48,000 --> 00:04:50,000
+Okay, so even if we don't call it, it will be called.
+
+128
+00:04:50,000 --> 00:04:51,000
+Now when it will be called,
+
+129
+00:04:51,000 --> 00:04:53,000
+every time you create an object,
+
+130
+00:04:53,000 --> 00:04:55,000
+it will call the constructor.
+
+131
+00:04:55,000 --> 00:04:57,000
+So every time you create the object,
+
+132
+00:04:57,000 --> 00:04:59,000
+it will call the constructor.
+
+133
+00:04:59,000 --> 00:05:01,000
+Example, let's say if I create two objects,
+
+134
+00:05:01,000 --> 00:05:02,000
+I will just copy this line and paste it here.
+
+135
+00:05:02,000 --> 00:05:04,000
+Of course, I should have a different name
+
+136
+00:05:04,000 --> 00:05:05,000
+for the difference OBJ 1.
+
+137
+00:05:05,000 --> 00:05:08,000
+Now you can see we have two objects.
+
+138
+00:05:08,000 --> 00:05:09,000
+Now, when you say you have two objects,
+
+139
+00:05:09,000 --> 00:05:12,000
+and if I try to compile and run this,
+
+140
+00:05:12,000 --> 00:05:14,000
+you can see we got in constructor two times.
+
+141
+00:05:14,000 --> 00:05:17,000
+So every time you create a new object,
+
+142
+00:05:17,000 --> 00:05:19,000
+it will create a constructor,
+
+143
+00:05:19,000 --> 00:05:20,000
+or it will call the constructor.
+
+144
+00:05:20,000 --> 00:05:22,000
+Okay, if that makes sense.
+
+145
+00:05:22,000 --> 00:05:24,000
+What we can do is if we can remove this line
+
+146
+00:05:24,000 --> 00:05:28,000
+and I can assign the values, I can say age is equal to 12,
+
+147
+00:05:28,000 --> 00:05:32,000
+and name is equal to let's say by default, John,
+
+148
+00:05:32,000 --> 00:05:35,000
+of course you can have any name, but let's say John.
+
+149
+00:05:35,000 --> 00:05:40,000
+Now in this case I can see if this values are assigned.
+
+150
+00:05:40,000 --> 00:05:42,000
+What I can also do is I can just command this section.
+
+151
+00:05:42,000 --> 00:05:44,000
+Let's say I'm not assigning the values.
+
+152
+00:05:44,000 --> 00:05:46,000
+Let's see what are default values?
+
+153
+00:05:46,000 --> 00:05:48,000
+Compile, run, you can see we got John and 12.
+
+154
+00:05:48,000 --> 00:05:52,000
+So by default you assign this value.
+
+155
+00:05:52,000 --> 00:05:55,000
+Okay, so this is where constructors are helpful.
+
+156
+00:05:55,000 --> 00:05:56,000
+Now, you might be thinking,
+
+157
+00:05:56,000 --> 00:05:59,000
+hey, we can assign values here itself, right?
+
+158
+00:05:59,000 --> 00:06:02,000
+See, there's a idea, there's a standards which we follow,
+
+159
+00:06:02,000 --> 00:06:05,000
+whenever you want to perform any operation,
+
+160
+00:06:05,000 --> 00:06:07,000
+always do that in a method.
+
+161
+00:06:07,000 --> 00:06:11,000
+Don't openly do it in the statement like here,
+
+162
+00:06:11,000 --> 00:06:13,000
+if you want to perform some operation, like assignment,
+
+163
+00:06:13,000 --> 00:06:16,000
+or calculation, always doing the methods.
+
+164
+00:06:16,000 --> 00:06:19,000
+And constructor is like method, right?
+
+165
+00:06:19,000 --> 00:06:20,000
+So you can assign the values here.
+
+166
+00:06:20,000 --> 00:06:23,000
+There's no harm in terms of compilation.
+
+167
+00:06:23,000 --> 00:06:25,000
+You can assign the value here as well.
+
+168
+00:06:25,000 --> 00:06:27,000
+But we have to follow standards, right?
+
+169
+00:06:27,000 --> 00:06:29,000
+And also just try to think about something at once.
+
+170
+00:06:29,000 --> 00:06:32,000
+Let's say you are trying to connect with a database.
+
+171
+00:06:32,000 --> 00:06:35,000
+Now in that scenario, your application
+
+172
+00:06:35,000 --> 00:06:38,000
+is trying to connect with our database or the network.
+
+173
+00:06:38,000 --> 00:06:40,000
+You need that connection right?
+
+174
+00:06:40,000 --> 00:06:42,000
+Now where you will write the connection?
+
+175
+00:06:42,000 --> 00:06:45,000
+You can write the connections in the constructor.
+
+176
+00:06:45,000 --> 00:06:47,000
+And that's why this becomes very important.
+
+177
+00:06:47,000 --> 00:06:48,000
+Now, if you remember,
+
+178
+00:06:48,000 --> 00:06:50,000
+we have also talked about method overloading.
+
+179
+00:06:50,000 --> 00:06:53,000
+So when you have two methods with the same name
+
+180
+00:06:53,000 --> 00:06:54,000
+but different parameters,
+
+181
+00:06:54,000 --> 00:06:56,000
+those are called method overloading.
+
+182
+00:06:56,000 --> 00:07:00,000
+Now can we do that in constructor? That's tricky, right?
+
+183
+00:07:00,000 --> 00:07:02,000
+So let's discuss that in the next video.
+
+184
+00:07:02,000 --> 00:07:05,000
+How do we achieve constructor overloading.
+
diff --git a/02 - Core Java/047 Source-code.url b/02 - Core Java/047 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/047 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/048 Default vs Parameterized Constructor_en.srt b/02 - Core Java/048 Default vs Parameterized Constructor_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..934d11ca8e36d14eca7a6cc0e7d151bc5a85c255
--- /dev/null
+++ b/02 - Core Java/048 Default vs Parameterized Constructor_en.srt	
@@ -0,0 +1,520 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: Okay, so now we know what is constructor, right?
+
+3
+00:00:05,000 --> 00:00:09,000
+But what about this? I mean, can I pass the values here?
+
+4
+00:00:09,000 --> 00:00:12,000
+What if I don't want to assign values like 12 and John?
+
+5
+00:00:12,000 --> 00:00:14,000
+What if I want to customize it?
+
+6
+00:00:14,000 --> 00:00:17,000
+So, what I want is every time I create the object,
+
+7
+00:00:17,000 --> 00:00:20,000
+I should have an option of passing those values,
+
+8
+00:00:20,000 --> 00:00:22,000
+not 12 and John every time.
+
+9
+00:00:22,000 --> 00:00:23,000
+Can we do that?
+
+10
+00:00:23,000 --> 00:00:24,000
+Of course, you can assign the values later
+
+11
+00:00:24,000 --> 00:00:26,000
+with the help of site methods,
+
+12
+00:00:26,000 --> 00:00:29,000
+but what if I have an idea where, hey, you know,
+
+13
+00:00:29,000 --> 00:00:31,000
+I, okay, let's go with this object, as well,
+
+14
+00:00:31,000 --> 00:00:33,000
+the second object.
+
+15
+00:00:33,000 --> 00:00:35,000
+And in the second object, I want to pass the values.
+
+16
+00:00:35,000 --> 00:00:37,000
+The first object, I want it to be default.
+
+17
+00:00:37,000 --> 00:00:40,000
+The second object, I want the age to be, let's say 18.
+
+18
+00:00:40,000 --> 00:00:44,000
+And the name should be let's say Navin. Can we do that?
+
+19
+00:00:44,000 --> 00:00:46,000
+If you can see, this line is giving you error.
+
+20
+00:00:46,000 --> 00:00:49,000
+It says, hey, you know you don't have a constructor
+
+21
+00:00:49,000 --> 00:00:51,000
+which accepts two values,
+
+22
+00:00:51,000 --> 00:00:53,000
+so those two values of type integer and string,
+
+23
+00:00:53,000 --> 00:00:54,000
+you don't have it.
+
+24
+00:00:54,000 --> 00:00:56,000
+And if you go up, actually, you don't have it.
+
+25
+00:00:56,000 --> 00:00:59,000
+You don't have a constructor which takes two parameters.
+
+26
+00:00:59,000 --> 00:01:01,000
+Can we do that? Let's try.
+
+27
+00:01:01,000 --> 00:01:03,000
+So, I will say public Human,
+
+28
+00:01:03,000 --> 00:01:06,000
+and I want this Human to take two parameters.
+
+29
+00:01:06,000 --> 00:01:11,000
+So I will say int a, String name
+
+30
+00:01:11,000 --> 00:01:13,000
+and then here, I can just come back
+
+31
+00:01:13,000 --> 00:01:15,000
+and I can say age is equal to a.
+
+32
+00:01:15,000 --> 00:01:18,000
+So, not the default value which I want to assign here.
+
+33
+00:01:18,000 --> 00:01:21,000
+I want to assign the value which is sent by the main method.
+
+34
+00:01:21,000 --> 00:01:25,000
+So, if you can see, we are passing 18 and Navin here, right?
+
+35
+00:01:25,000 --> 00:01:27,000
+So I can just go back here.
+
+36
+00:01:27,000 --> 00:01:30,000
+And age is equal to a. Name is equal to n.
+
+37
+00:01:30,000 --> 00:01:33,000
+Now if you look at this particular constructor here,
+
+38
+00:01:33,000 --> 00:01:35,000
+it is taking some parameter.
+
+39
+00:01:35,000 --> 00:01:38,000
+So this constructor is called a parameterized constructor.
+
+40
+00:01:38,000 --> 00:01:40,000
+Oh, I should say this is n.
+
+41
+00:01:40,000 --> 00:01:43,000
+Now, what is the difference between normal constructor
+
+42
+00:01:43,000 --> 00:01:45,000
+and a parameterized constructor is, in fact,
+
+43
+00:01:45,000 --> 00:01:47,000
+this normal constructor is also called
+
+44
+00:01:47,000 --> 00:01:49,000
+a default constructor.
+
+45
+00:01:49,000 --> 00:01:51,000
+Now we'll discuss why this called default constructor.
+
+46
+00:01:51,000 --> 00:01:53,000
+So, this is called a default constructor.
+
+47
+00:01:53,000 --> 00:01:56,000
+This is called a parameterized constructor
+
+48
+00:01:56,000 --> 00:01:57,000
+because we have parameters there.
+
+49
+00:01:57,000 --> 00:02:00,000
+And whatever value you pass here will be assigned.
+
+50
+00:02:00,000 --> 00:02:01,000
+Now, you can use both syntax.
+
+51
+00:02:01,000 --> 00:02:03,000
+You can either create an object
+
+52
+00:02:03,000 --> 00:02:06,000
+by not specifying any parameter or arguments,
+
+53
+00:02:06,000 --> 00:02:11,000
+and you can create a object with the help of values,
+
+54
+00:02:11,000 --> 00:02:13,000
+which we are passing it here.
+
+55
+00:02:13,000 --> 00:02:16,000
+So, this is parameterized and this is default.
+
+56
+00:02:16,000 --> 00:02:17,000
+Now what I will do just to explain this,
+
+57
+00:02:17,000 --> 00:02:20,000
+is I will just copy the same line
+
+58
+00:02:20,000 --> 00:02:23,000
+and I will print the values for obj1 this time,
+
+59
+00:02:23,000 --> 00:02:24,000
+not for obj, obj1.
+
+60
+00:02:24,000 --> 00:02:26,000
+So basically, we are printing both
+
+61
+00:02:26,000 --> 00:02:27,000
+and let's see what the output is.
+
+62
+00:02:27,000 --> 00:02:29,000
+Compile, run.
+
+63
+00:02:29,000 --> 00:02:32,000
+You can see we got the first object, John : 12.
+
+64
+00:02:32,000 --> 00:02:33,000
+The second object is not John and 12.
+
+65
+00:02:33,000 --> 00:02:35,000
+It is Navin and 18
+
+66
+00:02:35,000 --> 00:02:36,000
+because you are passing those values.
+
+67
+00:02:36,000 --> 00:02:38,000
+Now what I will do this time and I will remove this part
+
+68
+00:02:38,000 --> 00:02:40,000
+just to explain you something.
+
+69
+00:02:40,000 --> 00:02:42,000
+See, when I mentioned that every time,
+
+70
+00:02:42,000 --> 00:02:44,000
+let me just commend this section, as well.
+
+71
+00:02:44,000 --> 00:02:47,000
+See, every time you create the object,
+
+72
+00:02:47,000 --> 00:02:50,000
+it will call the constructor, right?
+
+73
+00:02:50,000 --> 00:02:52,000
+But then if you see, I have removed the constructor.
+
+74
+00:02:52,000 --> 00:02:53,000
+Will this work?
+
+75
+00:02:53,000 --> 00:02:55,000
+And it was working before.
+
+76
+00:02:55,000 --> 00:02:56,000
+Remember when we started this example of Human,
+
+77
+00:02:56,000 --> 00:02:58,000
+we were not having any constructor.
+
+78
+00:02:58,000 --> 00:03:00,000
+It was still working.
+
+79
+00:03:00,000 --> 00:03:03,000
+At this point, your Java will say, hey, don't worry.
+
+80
+00:03:03,000 --> 00:03:05,000
+If you don't mention constructor there,
+
+81
+00:03:05,000 --> 00:03:07,000
+I will create a constructor for you.
+
+82
+00:03:07,000 --> 00:03:10,000
+And that's why we say that's a default constructor.
+
+83
+00:03:10,000 --> 00:03:13,000
+So behind the scene, you will get this constructor here,
+
+84
+00:03:13,000 --> 00:03:15,000
+which is public Human.
+
+85
+00:03:15,000 --> 00:03:18,000
+This is what you will get even if you don't mention, okay?
+
+86
+00:03:18,000 --> 00:03:20,000
+The only thing is it will be default.
+
+87
+00:03:20,000 --> 00:03:22,000
+It will be blank if you don't mention.
+
+88
+00:03:22,000 --> 00:03:23,000
+But if you want to do something, of course,
+
+89
+00:03:23,000 --> 00:03:25,000
+you have to mention that explicitly.
+
+90
+00:03:25,000 --> 00:03:27,000
+And we can use the same code
+
+91
+00:03:27,000 --> 00:03:31,000
+or I can actually ask my IDE to give me the code.
+
+92
+00:03:31,000 --> 00:03:34,000
+So, you can simply go to Source and Action
+
+93
+00:03:34,000 --> 00:03:37,000
+and you can say, hey, I want to create a constructor,
+
+94
+00:03:37,000 --> 00:03:38,000
+but which constructor?
+
+95
+00:03:38,000 --> 00:03:41,000
+So, I want a constructor which takes both these arguments.
+
+96
+00:03:41,000 --> 00:03:44,000
+And I also want a default constructor.
+
+97
+00:03:44,000 --> 00:03:46,000
+Source Action.
+
+98
+00:03:46,000 --> 00:03:48,000
+I want a constructor which is default.
+
+99
+00:03:48,000 --> 00:03:51,000
+You can see we got two constructors.
+
+100
+00:03:51,000 --> 00:03:52,000
+There's only one change.
+
+101
+00:03:52,000 --> 00:03:56,000
+The syntax which we have return was a and name,
+
+102
+00:03:56,000 --> 00:03:58,000
+and here if you can see, we have age and name.
+
+103
+00:03:58,000 --> 00:04:01,000
+And to make it work, we have to use this keyword.
+
+104
+00:04:01,000 --> 00:04:03,000
+I hope you remember this keyword video previously.
+
+105
+00:04:03,000 --> 00:04:06,000
+And that's how it works. It has the same way which works.
+
+106
+00:04:06,000 --> 00:04:08,000
+The only thing is we have to assign the values here.
+
+107
+00:04:08,000 --> 00:04:13,000
+I will say age is equal to 12 and the name is John.
+
+108
+00:04:13,000 --> 00:04:16,000
+So, that's how we can basically use a default constructor
+
+109
+00:04:16,000 --> 00:04:17,000
+and a parameterized constructor.
+
+110
+00:04:17,000 --> 00:04:19,000
+Of course, we can create some more constructor here.
+
+111
+00:04:19,000 --> 00:04:22,000
+What if you want to just specify the name,
+
+112
+00:04:22,000 --> 00:04:23,000
+not the role number?
+
+113
+00:04:23,000 --> 00:04:28,000
+So you can say, I want a constructor, Source Action,
+
+114
+00:04:29,000 --> 00:04:32,000
+and I want a constructor which takes only name.
+
+115
+00:04:32,000 --> 00:04:33,000
+So you can see we've got a constructor
+
+116
+00:04:33,000 --> 00:04:34,000
+which only takes a name.
+
+117
+00:04:34,000 --> 00:04:36,000
+Now what happens to this type of objects?
+
+118
+00:04:36,000 --> 00:04:38,000
+Example, if I create an object here,
+
+119
+00:04:38,000 --> 00:04:39,000
+let's say the second object,
+
+120
+00:04:39,000 --> 00:04:41,000
+and this time I'm not passing two values.
+
+121
+00:04:41,000 --> 00:04:43,000
+I'm just passing one value, which is name.
+
+122
+00:04:43,000 --> 00:04:47,000
+In this case, the age will be zero.
+
+123
+00:04:47,000 --> 00:04:49,000
+So what you can do is even if you're accepting name,
+
+124
+00:04:49,000 --> 00:04:52,000
+you can assign the age by year, so we can say 12.
+
+125
+00:04:52,000 --> 00:04:53,000
+You can say age because there's no confusion
+
+126
+00:04:53,000 --> 00:04:55,000
+or you can also say this.age
+
+127
+00:04:55,000 --> 00:04:57,000
+just to maintain the uniformity.
+
+128
+00:04:57,000 --> 00:05:00,000
+Okay, so that's how we use constructors,
+
+129
+00:05:00,000 --> 00:05:03,000
+default constructors, parameterized constructors,
+
+130
+00:05:03,000 --> 00:05:04,000
+and yeah, that's it.
+
diff --git a/02 - Core Java/048 Source-code.url b/02 - Core Java/048 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/048 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/049 Naming Convention_en.srt b/02 - Core Java/049 Naming Convention_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..fe08b81a92d3b942ee3db68553842c9dfc3da6a8
--- /dev/null
+++ b/02 - Core Java/049 Naming Convention_en.srt	
@@ -0,0 +1,440 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, let's talk about the naming conventions.
+
+3
+00:00:06,000 --> 00:00:08,000
+Now, if you see the code which we are written till now,
+
+4
+00:00:08,000 --> 00:00:11,000
+somewhere, I was using capital letters,
+
+5
+00:00:11,000 --> 00:00:13,000
+I was using small letters.
+
+6
+00:00:13,000 --> 00:00:14,000
+When to use what?
+
+7
+00:00:14,000 --> 00:00:17,000
+And then what if you want to join two words?
+
+8
+00:00:17,000 --> 00:00:19,000
+How will you make it more readable?
+
+9
+00:00:19,000 --> 00:00:21,000
+Now that's where Java says it follows a naming convention
+
+10
+00:00:21,000 --> 00:00:22,000
+of camel casing.
+
+11
+00:00:22,000 --> 00:00:26,000
+So basically, it uses camel casing.
+
+12
+00:00:26,000 --> 00:00:27,000
+Now, what camel casing means,
+
+13
+00:00:27,000 --> 00:00:30,000
+or let's talk about in general how do we name our classes?
+
+14
+00:00:30,000 --> 00:00:32,000
+Now, whenever you create a class,
+
+15
+00:00:32,000 --> 00:00:34,000
+a class name should start with a capital letter.
+
+16
+00:00:34,000 --> 00:00:36,000
+So when you talk about class,
+
+17
+00:00:36,000 --> 00:00:37,000
+it should start with a capital letter.
+
+18
+00:00:37,000 --> 00:00:40,000
+Example, if you want to get a class called Calculator,
+
+19
+00:00:40,000 --> 00:00:41,000
+the C should be capital.
+
+20
+00:00:41,000 --> 00:00:44,000
+Now on the other hand, if you talk about variables
+
+21
+00:00:44,000 --> 00:00:48,000
+or methods, so for variable and methods,
+
+22
+00:00:48,000 --> 00:00:52,000
+what you will follow is you will start with a small letter.
+
+23
+00:00:52,000 --> 00:00:54,000
+Example, if your variable name can be marks,
+
+24
+00:00:54,000 --> 00:00:56,000
+a method name can be show.
+
+25
+00:00:56,000 --> 00:00:58,000
+So, it will always start with small.
+
+26
+00:00:58,000 --> 00:01:02,000
+Class, capital, variable, method, small.
+
+27
+00:01:02,000 --> 00:01:04,000
+In fact, we also have a concept of interfaces,
+
+28
+00:01:04,000 --> 00:01:05,000
+which we'll discuss later.
+
+29
+00:01:05,000 --> 00:01:08,000
+So if we talk about classes and interface,
+
+30
+00:01:08,000 --> 00:01:10,000
+we'll have to make it capital.
+
+31
+00:01:10,000 --> 00:01:12,000
+Let's say interface is Runable.
+
+32
+00:01:12,000 --> 00:01:14,000
+So basically, this is the convention which we follow.
+
+33
+00:01:14,000 --> 00:01:17,000
+Class, interface, we have capital letters,
+
+34
+00:01:17,000 --> 00:01:19,000
+variable, methods, we have small letters.
+
+35
+00:01:19,000 --> 00:01:21,000
+We also have a concept of constants,
+
+36
+00:01:21,000 --> 00:01:23,000
+which we have talked about.
+
+37
+00:01:23,000 --> 00:01:27,000
+So when you talk about constants, it will have a capital,
+
+38
+00:01:27,000 --> 00:01:28,000
+but all capital.
+
+39
+00:01:28,000 --> 00:01:30,000
+Example, if we talk about the value of PIE,
+
+40
+00:01:30,000 --> 00:01:34,000
+if we talk about a constant of BRAND,
+
+41
+00:01:34,000 --> 00:01:35,000
+so doesn't matter what your constant is.
+
+42
+00:01:35,000 --> 00:01:39,000
+So you can have all capital here. Now, why do we do this?
+
+43
+00:01:39,000 --> 00:01:41,000
+We do this just to see and understand
+
+44
+00:01:41,000 --> 00:01:43,000
+what could be the thing which you are doing.
+
+45
+00:01:43,000 --> 00:01:46,000
+Example, if you say, if you see this type of things,
+
+46
+00:01:46,000 --> 00:01:49,000
+you can guess, hey, it can be a class or interface.
+
+47
+00:01:49,000 --> 00:01:52,000
+If you look at this, you know this is a variable.
+
+48
+00:01:52,000 --> 00:01:54,000
+If you look at this, you know this is a method.
+
+49
+00:01:54,000 --> 00:01:57,000
+And when you look at this, you know these are constants.
+
+50
+00:01:57,000 --> 00:01:59,000
+It makes your code much more readable.
+
+51
+00:01:59,000 --> 00:02:00,000
+And that's important, right?
+
+52
+00:02:00,000 --> 00:02:03,000
+It's very easy to write a code which works.
+
+53
+00:02:03,000 --> 00:02:05,000
+It's difficult to write a code which anyone can read,
+
+54
+00:02:05,000 --> 00:02:08,000
+and that's why you should follow this convention.
+
+55
+00:02:08,000 --> 00:02:11,000
+So, this is how you use the main convention.
+
+56
+00:02:11,000 --> 00:02:14,000
+But what if you have a word which which has two letters?
+
+57
+00:02:14,000 --> 00:02:17,000
+Example, if you talk about, show my marks.
+
+58
+00:02:17,000 --> 00:02:21,000
+If I want to do this, so you have to say, showMyMarks,
+
+59
+00:02:21,000 --> 00:02:24,000
+because if you say showmymarks,
+
+60
+00:02:24,000 --> 00:02:27,000
+it is actually a bit difficult to read, right?
+
+61
+00:02:27,000 --> 00:02:30,000
+So what you can do is every time you combine words,
+
+62
+00:02:30,000 --> 00:02:31,000
+make sure that the first letter of the second word
+
+63
+00:02:31,000 --> 00:02:34,000
+or the first letter make it capital.
+
+64
+00:02:34,000 --> 00:02:37,000
+It makes it much more readable compared to small letters.
+
+65
+00:02:37,000 --> 00:02:39,000
+Now, this is what camel casing means.
+
+66
+00:02:39,000 --> 00:02:41,000
+You know we have camel, so it goes up and down.
+
+67
+00:02:41,000 --> 00:02:45,000
+So we have small letters, then we have in between,
+
+68
+00:02:45,000 --> 00:02:47,000
+we have capital, small, again, we have capital.
+
+69
+00:02:47,000 --> 00:02:49,000
+So this is camel casing.
+
+70
+00:02:49,000 --> 00:02:51,000
+Now, apart from this, there are different languages
+
+71
+00:02:51,000 --> 00:02:53,000
+which follow snake casing rule
+
+72
+00:02:53,000 --> 00:02:54,000
+where we use underscores.
+
+73
+00:02:54,000 --> 00:02:58,000
+Example, in some languages, they follow snake casing.
+
+74
+00:02:58,000 --> 00:02:59,000
+They use underscore.
+
+75
+00:02:59,000 --> 00:03:01,000
+And people who jump between different languages,
+
+76
+00:03:01,000 --> 00:03:04,000
+they get this tendency of using underscore.
+
+77
+00:03:04,000 --> 00:03:06,000
+So, again, Java will not give you any error,
+
+78
+00:03:06,000 --> 00:03:08,000
+but if you follow the Java pattern,
+
+79
+00:03:08,000 --> 00:03:10,000
+Java developers will not like this.
+
+80
+00:03:10,000 --> 00:03:12,000
+So, if you're writing a code where you have a Java team
+
+81
+00:03:12,000 --> 00:03:15,000
+or everyone who works on Java, try to follow camel casing
+
+82
+00:03:15,000 --> 00:03:18,000
+and, but again, it will not give you error.
+
+83
+00:03:18,000 --> 00:03:19,000
+It perfectly works.
+
+84
+00:03:19,000 --> 00:03:22,000
+Underscore works in the names, but that's what we follow.
+
+85
+00:03:22,000 --> 00:03:26,000
+We follow camel casing here, not snake casing, yeah?
+
+86
+00:03:26,000 --> 00:03:29,000
+If you have the class name, which is again,
+
+87
+00:03:29,000 --> 00:03:32,000
+I want to say MyData is a class,
+
+88
+00:03:32,000 --> 00:03:36,000
+so you can say M is capital because that's a class name.
+
+89
+00:03:36,000 --> 00:03:38,000
+Now I will give you, I will show you some names
+
+90
+00:03:38,000 --> 00:03:40,000
+and you have to guess what those are.
+
+91
+00:03:40,000 --> 00:03:44,000
+Example, if I say age, that's variable, right, okay?
+
+92
+00:03:44,000 --> 00:03:47,000
+What if I say DATA? What is this?
+
+93
+00:03:47,000 --> 00:03:51,000
+This is a constant because everything is capital, okay?
+
+94
+00:03:51,000 --> 00:03:54,000
+Yeah, in terms of constant, if you want to say my data,
+
+95
+00:03:54,000 --> 00:03:56,000
+which is a constant, you have to use MYDATA,
+
+96
+00:03:56,000 --> 00:03:58,000
+but again, everything is capital, right?
+
+97
+00:03:58,000 --> 00:03:59,000
+So at this point, you can use underscore
+
+98
+00:03:59,000 --> 00:04:02,000
+just to differentiate this, and again,
+
+99
+00:04:02,000 --> 00:04:03,000
+these are the good practices which I'm showing you.
+
+100
+00:04:03,000 --> 00:04:04,000
+How about this?
+
+101
+00:04:04,000 --> 00:04:08,000
+If I use something like Human, but I use a round bracket.
+
+102
+00:04:08,000 --> 00:04:10,000
+Any guess? Yeah, that's a constructor.
+
+103
+00:04:10,000 --> 00:04:11,000
+Why is a constructor?
+
+104
+00:04:11,000 --> 00:04:14,000
+Is because the first letter is capital.
+
+105
+00:04:14,000 --> 00:04:16,000
+That means it represents a class name.
+
+106
+00:04:16,000 --> 00:04:17,000
+And we also have a round bracket,
+
+107
+00:04:17,000 --> 00:04:20,000
+method like something, so that's a constructor.
+
+108
+00:04:20,000 --> 00:04:22,000
+So this is a naming convention which we follow
+
+109
+00:04:22,000 --> 00:04:25,000
+and try to use good names for your variables, your classes,
+
+110
+00:04:25,000 --> 00:04:29,000
+your methods, so that it will be easy for others to read.
+
diff --git a/02 - Core Java/049 Source-code.url b/02 - Core Java/049 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/049 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/050 Anonymous Object_en.srt b/02 - Core Java/050 Anonymous Object_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..b9e03946b017737b8704a88a2bab04417465ac2e
--- /dev/null
+++ b/02 - Core Java/050 Anonymous Object_en.srt	
@@ -0,0 +1,508 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle piano music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: Okay, so now we know how to create the object, right?
+
+3
+00:00:05,000 --> 00:00:06,000
+So we have a class.
+
+4
+00:00:06,000 --> 00:00:08,000
+Let's say we have a class A,
+
+5
+00:00:08,000 --> 00:00:10,000
+and then in this class A, we have a show method.
+
+6
+00:00:10,000 --> 00:00:11,000
+Now, how do we call show method?
+
+7
+00:00:11,000 --> 00:00:12,000
+That's very simple.
+
+8
+00:00:12,000 --> 00:00:14,000
+First you have to create the object of A,
+
+9
+00:00:14,000 --> 00:00:16,000
+and then you can call the show method.
+
+10
+00:00:16,000 --> 00:00:17,000
+Now what happens behind the scenes?
+
+11
+00:00:17,000 --> 00:00:21,000
+So of course you have your big JVM here,
+
+12
+00:00:21,000 --> 00:00:24,000
+and then in this you'll be having your stack memory
+
+13
+00:00:24,000 --> 00:00:26,000
+and then you'll be having your heap memory as well.
+
+14
+00:00:26,000 --> 00:00:29,000
+Now, in this heap memory, so if you look at line number 14,
+
+15
+00:00:29,000 --> 00:00:31,000
+it will create an object.
+
+16
+00:00:31,000 --> 00:00:33,000
+Let's say the address is 1 0 1,
+
+17
+00:00:33,000 --> 00:00:36,000
+and then in this you'll be having a variable or methods.
+
+18
+00:00:36,000 --> 00:00:37,000
+We don't have a variable as of now.
+
+19
+00:00:37,000 --> 00:00:39,000
+So let's say we have a method which is show.
+
+20
+00:00:39,000 --> 00:00:41,000
+So of course in order to call this show, we need objects.
+
+21
+00:00:41,000 --> 00:00:44,000
+So we have done that, and then we have OBJ here.
+
+22
+00:00:44,000 --> 00:00:48,000
+The address will be 1 0 1 and it will refer here.
+
+23
+00:00:48,000 --> 00:00:50,000
+And then every time you want to call show,
+
+24
+00:00:50,000 --> 00:00:54,000
+basically you have to say obj.show.
+
+25
+00:00:54,000 --> 00:00:56,000
+That's how it works, right? Okay.
+
+26
+00:00:56,000 --> 00:00:58,000
+Now just to clear the things,
+
+27
+00:00:58,000 --> 00:01:01,000
+this OBJ here is not called the object.
+
+28
+00:01:01,000 --> 00:01:04,000
+It is called a reference variable, right?
+
+29
+00:01:04,000 --> 00:01:07,000
+So this is your reference variable.
+
+30
+00:01:07,000 --> 00:01:08,000
+Why this called a reference variable?
+
+31
+00:01:08,000 --> 00:01:09,000
+Because it's referring to an object.
+
+32
+00:01:09,000 --> 00:01:10,000
+The object is here.
+
+33
+00:01:10,000 --> 00:01:13,000
+So this is your object, okay?
+
+34
+00:01:13,000 --> 00:01:15,000
+So the question is, if I want to create this object,
+
+35
+00:01:15,000 --> 00:01:18,000
+is this line compulsory or do we have a shortcut?
+
+36
+00:01:18,000 --> 00:01:19,000
+Now to understand this mode,
+
+37
+00:01:19,000 --> 00:01:21,000
+let's also use a concept of constructor.
+
+38
+00:01:21,000 --> 00:01:23,000
+So let's say we have a constructor here, which is A,
+
+39
+00:01:23,000 --> 00:01:26,000
+and then I'm just trying to print something here,
+
+40
+00:01:26,000 --> 00:01:28,000
+it says object created.
+
+41
+00:01:28,000 --> 00:01:30,000
+So of course we know every time you create the object,
+
+42
+00:01:30,000 --> 00:01:33,000
+it will call the constructor as well.
+
+43
+00:01:33,000 --> 00:01:33,000
+So it should print.
+
+44
+00:01:33,000 --> 00:01:36,000
+So if I compile and run this code,
+
+45
+00:01:36,000 --> 00:01:38,000
+you can see it says object created
+
+46
+00:01:38,000 --> 00:01:40,000
+and it is printing in a show.
+
+47
+00:01:40,000 --> 00:01:42,000
+Now, actually, if you look at this line here,
+
+48
+00:01:42,000 --> 00:01:44,000
+there are two steps, not one.
+
+49
+00:01:44,000 --> 00:01:46,000
+Example, so let's say if you create
+
+50
+00:01:46,000 --> 00:01:49,000
+a local variable called marks, okay?
+
+51
+00:01:49,000 --> 00:01:51,000
+And then you set the marks for it,
+
+52
+00:01:51,000 --> 00:01:52,000
+you set the value for it.
+
+53
+00:01:52,000 --> 00:01:54,000
+Let's say 99,
+
+54
+00:01:54,000 --> 00:01:56,000
+we hate, everyone hates this type of people, right?
+
+55
+00:01:56,000 --> 00:01:58,000
+Anyway, so we have this variable.
+
+56
+00:01:58,000 --> 00:02:00,000
+So what we are doing is we are first of all
+
+57
+00:02:00,000 --> 00:02:04,000
+declaring the variable and then we are as assigning a value.
+
+58
+00:02:04,000 --> 00:02:06,000
+The same thing can be done for this thing, right?
+
+59
+00:02:06,000 --> 00:02:08,000
+We can do it in two steps.
+
+60
+00:02:08,000 --> 00:02:09,000
+We can declare the object
+
+61
+00:02:09,000 --> 00:02:13,000
+and then we can say OBJ equal to new A.
+
+62
+00:02:13,000 --> 00:02:15,000
+Now this is called reference creation, right?
+
+63
+00:02:15,000 --> 00:02:17,000
+This is where you're creating a reference and then
+
+64
+00:02:17,000 --> 00:02:19,000
+this is where you are creating an object
+
+65
+00:02:19,000 --> 00:02:23,000
+and assigning the value to OBJ.
+
+66
+00:02:23,000 --> 00:02:26,000
+That means this is, I mean, when you say new A,
+
+67
+00:02:26,000 --> 00:02:29,000
+this is where you create the object.
+
+68
+00:02:29,000 --> 00:02:30,000
+Let me show that.
+
+69
+00:02:30,000 --> 00:02:35,000
+Let me remove everything from here and say new A,
+
+70
+00:02:35,000 --> 00:02:38,000
+this is object creation, not the entire line.
+
+71
+00:02:38,000 --> 00:02:41,000
+When you say new A constructor,
+
+72
+00:02:41,000 --> 00:02:43,000
+that is your object creation.
+
+73
+00:02:43,000 --> 00:02:45,000
+The moment you do that in your heap memory,
+
+74
+00:02:45,000 --> 00:02:48,000
+of course we don't have all this data now,
+
+75
+00:02:48,000 --> 00:02:50,000
+so ignore all this data, which is there,
+
+76
+00:02:50,000 --> 00:02:52,000
+let me just remove this. This is not there.
+
+77
+00:02:52,000 --> 00:02:53,000
+Imagine there's no object.
+
+78
+00:02:53,000 --> 00:02:55,000
+So this line will create an object,
+
+79
+00:02:55,000 --> 00:02:58,000
+doesn't matter what's the address. Let's say 5 0 1,
+
+80
+00:02:58,000 --> 00:03:01,000
+and it will have this show method, okay?
+
+81
+00:03:01,000 --> 00:03:04,000
+The only thing is we are not doing anything.
+
+82
+00:03:04,000 --> 00:03:06,000
+We are not creating any variable inside stack.
+
+83
+00:03:06,000 --> 00:03:10,000
+Example, when you say int marks, the moment you do that,
+
+84
+00:03:10,000 --> 00:03:13,000
+it will create a int variable called marks, here.
+
+85
+00:03:13,000 --> 00:03:15,000
+The value will be blank.
+
+86
+00:03:15,000 --> 00:03:17,000
+And whatever value you want to assign,
+
+87
+00:03:17,000 --> 00:03:18,000
+you can assign that here.
+
+88
+00:03:18,000 --> 00:03:20,000
+But if you can see, we are not doing anything here.
+
+89
+00:03:20,000 --> 00:03:22,000
+We are just creating a object,
+
+90
+00:03:22,000 --> 00:03:26,000
+that is created inside the heap memory, nothing in stack.
+
+91
+00:03:26,000 --> 00:03:29,000
+And if you don't trust me, let me just show you the proof.
+
+92
+00:03:29,000 --> 00:03:34,000
+If I compile this code and run, it says object created.
+
+93
+00:03:34,000 --> 00:03:36,000
+This is the object,
+
+94
+00:03:36,000 --> 00:03:40,000
+and this type of objects are called anonymous object.
+
+95
+00:03:40,000 --> 00:03:40,000
+You know why?
+
+96
+00:03:40,000 --> 00:03:43,000
+It's because this type of object don't have a name, right?
+
+97
+00:03:43,000 --> 00:03:45,000
+What do you call when you have a reference?
+
+98
+00:03:45,000 --> 00:03:47,000
+It is called a referenced object.
+
+99
+00:03:47,000 --> 00:03:49,000
+Okay, because there's a reference in this stack.
+
+100
+00:03:49,000 --> 00:03:51,000
+So when you say OBJ, there's a reference here.
+
+101
+00:03:51,000 --> 00:03:54,000
+For the anonymous object, there is no reference.
+
+102
+00:03:54,000 --> 00:03:56,000
+The only problem with this type of object is
+
+103
+00:03:56,000 --> 00:03:58,000
+you can't reuse them. Once you have written this line,
+
+104
+00:03:58,000 --> 00:04:02,000
+you got the new object in the heap, how will you use it?
+
+105
+00:04:02,000 --> 00:04:03,000
+That's the problem, right?
+
+106
+00:04:03,000 --> 00:04:04,000
+So you should use this type of object
+
+107
+00:04:04,000 --> 00:04:05,000
+only when it's required.
+
+108
+00:04:05,000 --> 00:04:08,000
+So let's say if you want to call show,
+
+109
+00:04:08,000 --> 00:04:09,000
+you can actually call this, okay?
+
+110
+00:04:09,000 --> 00:04:12,000
+So you can say new A,
+
+111
+00:04:12,000 --> 00:04:13,000
+dot show.
+
+112
+00:04:13,000 --> 00:04:15,000
+This is object, right? This is object.
+
+113
+00:04:15,000 --> 00:04:17,000
+So using the object you can call show.
+
+114
+00:04:17,000 --> 00:04:21,000
+The only thing is you can't use the same object again.
+
+115
+00:04:21,000 --> 00:04:24,000
+So if I compile and run, it worked.
+
+116
+00:04:24,000 --> 00:04:28,000
+The only thing is you can't use this object once more.
+
+117
+00:04:28,000 --> 00:04:30,000
+So if you write this line once more, what will happen?
+
+118
+00:04:30,000 --> 00:04:33,000
+Now, I mentioned that you can't reuse it.
+
+119
+00:04:33,000 --> 00:04:34,000
+What happens when you do that?
+
+120
+00:04:34,000 --> 00:04:36,000
+You can see it says object created.
+
+121
+00:04:36,000 --> 00:04:38,000
+So it has created two objects.
+
+122
+00:04:38,000 --> 00:04:43,000
+Every time you say new A, it creates a new object.
+
+123
+00:04:43,000 --> 00:04:45,000
+So wherever you want to use a normal object,
+
+124
+00:04:45,000 --> 00:04:47,000
+you can use this other objects.
+
+125
+00:04:47,000 --> 00:04:48,000
+Okay, so that's it.
+
+126
+00:04:48,000 --> 00:04:49,000
+That's it from this video
+
+127
+00:04:49,000 --> 00:04:51,000
+where we talked about anonymous objects.
+
diff --git a/02 - Core Java/050 Source-code.url b/02 - Core Java/050 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/050 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/051 Source-code.url b/02 - Core Java/051 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/051 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/051 What is Inheritance_en.srt b/02 - Core Java/051 What is Inheritance_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..2f2099aa473149cb548b38d73cd3cd051cac36cb
--- /dev/null
+++ b/02 - Core Java/051 What is Inheritance_en.srt	
@@ -0,0 +1,848 @@
+1
+00:00:00,000 --> 00:00:02,000
+(gentle music)
+
+2
+00:00:03,000 --> 00:00:04,000
+-: So in theory, we have talked
+
+3
+00:00:04,000 --> 00:00:06,000
+about what is inheritance, right?
+
+4
+00:00:06,000 --> 00:00:09,000
+Basically, you can just use the features of a superclass.
+
+5
+00:00:09,000 --> 00:00:12,000
+Let's try to implement that in this code.
+
+6
+00:00:12,000 --> 00:00:13,000
+Of course, we'll not be working with Humans anymore.
+
+7
+00:00:13,000 --> 00:00:18,000
+Let me just remove the entire code from here, and all gone.
+
+8
+00:00:18,000 --> 00:00:22,000
+And let me also make sure that this is empty, gone.
+
+9
+00:00:22,000 --> 00:00:24,000
+So we have a very simple method, which is main here.
+
+10
+00:00:24,000 --> 00:00:26,000
+Now what I wanna do is I want
+
+11
+00:00:26,000 --> 00:00:28,000
+to take the same example of calculator here.
+
+12
+00:00:28,000 --> 00:00:30,000
+So let me get a class called Calc,
+
+13
+00:00:30,000 --> 00:00:32,000
+and of course, I can just create this thing
+
+14
+00:00:32,000 --> 00:00:35,000
+in some other files as well, that actually makes sense.
+
+15
+00:00:35,000 --> 00:00:39,000
+But just to keep it simple, I'm using the same file here.
+
+16
+00:00:39,000 --> 00:00:41,000
+So we got a class called calculator,
+
+17
+00:00:41,000 --> 00:00:43,000
+and in this, I can add some methods and some variables.
+
+18
+00:00:43,000 --> 00:00:46,000
+So let's say I will define some methods here,
+
+19
+00:00:46,000 --> 00:00:49,000
+and I'll say public int, it can add two numbers.
+
+20
+00:00:49,000 --> 00:00:53,000
+It will accept two integers as well, I would say n1, n2.
+
+21
+00:00:53,000 --> 00:00:55,000
+So we got two variables, right?
+
+22
+00:00:55,000 --> 00:01:00,000
+And then I can just return n1 + n2, okay?
+
+23
+00:01:00,000 --> 00:01:03,000
+Now let's say in this calculator, we have two methods.
+
+24
+00:01:03,000 --> 00:01:08,000
+One is add and one is sub, which is sub here.
+
+25
+00:01:08,000 --> 00:01:09,000
+And there will be a subtraction operation.
+
+26
+00:01:09,000 --> 00:01:11,000
+So we got two methods, right?
+
+27
+00:01:11,000 --> 00:01:14,000
+Now one thing to remember, if you look at our File Explorer,
+
+28
+00:01:14,000 --> 00:01:17,000
+every time you get a file, it also creates a class file.
+
+29
+00:01:17,000 --> 00:01:20,000
+So for every class in your code, it will have a class files.
+
+30
+00:01:20,000 --> 00:01:24,000
+We have used a Calculator, a Computer,
+
+31
+00:01:24,000 --> 00:01:25,000
+Human, Student before,
+
+32
+00:01:25,000 --> 00:01:27,000
+and that's why we have all these classes.
+
+33
+00:01:27,000 --> 00:01:29,000
+What I will do is I will just delete them.
+
+34
+00:01:29,000 --> 00:01:31,000
+Okay, so you can see all these classes are gone.
+
+35
+00:01:31,000 --> 00:01:33,000
+In fact, let me also delete the Demo one
+
+36
+00:01:33,000 --> 00:01:34,000
+to see what happens.
+
+37
+00:01:34,000 --> 00:01:36,000
+And that's fine, you can also delete,
+
+38
+00:01:36,000 --> 00:01:37,000
+you can delete all the class files.
+
+39
+00:01:37,000 --> 00:01:39,000
+So every time you compile the code,
+
+40
+00:01:39,000 --> 00:01:40,000
+it will also create a class files for you.
+
+41
+00:01:40,000 --> 00:01:42,000
+Let me show you that.
+
+42
+00:01:42,000 --> 00:01:45,000
+So I will say javac, and if I mention the file name,
+
+43
+00:01:45,000 --> 00:01:49,000
+which is Demo.java, the moment I say Enter,
+
+44
+00:01:49,000 --> 00:01:50,000
+it will create two class files
+
+45
+00:01:50,000 --> 00:01:51,000
+because we have two classes.
+
+46
+00:01:51,000 --> 00:01:55,000
+If I go to Explorer, you can see we got Demo.class,
+
+47
+00:01:55,000 --> 00:01:57,000
+and we also have Calc.class.
+
+48
+00:01:57,000 --> 00:01:59,000
+Now when you run this code, if you say java,
+
+49
+00:01:59,000 --> 00:02:02,000
+and if you say Demo, it will just run the class files.
+
+50
+00:02:02,000 --> 00:02:04,000
+And as you can see,
+
+51
+00:02:04,000 --> 00:02:07,000
+we don't have any code here for calculator.
+
+52
+00:02:07,000 --> 00:02:11,000
+It will only run the Demo class, and that's how it works.
+
+53
+00:02:11,000 --> 00:02:14,000
+So if I just try to write this code here,
+
+54
+00:02:14,000 --> 00:02:18,000
+which we already have, and if I try to create object of it,
+
+55
+00:02:18,000 --> 00:02:19,000
+let's try creating object of it.
+
+56
+00:02:19,000 --> 00:02:22,000
+In fact, let me do one more thing before we start.
+
+57
+00:02:22,000 --> 00:02:25,000
+For this example, let me cut this part,
+
+58
+00:02:25,000 --> 00:02:30,000
+and create a new file and let me say this is Calc.java.
+
+59
+00:02:31,000 --> 00:02:35,000
+And yes, we have this code here.
+
+60
+00:02:35,000 --> 00:02:37,000
+So you can see now we have two files, and before I continue,
+
+61
+00:02:37,000 --> 00:02:40,000
+I will just delete these class files again.
+
+62
+00:02:40,000 --> 00:02:41,000
+Okay, class file deleted.
+
+63
+00:02:41,000 --> 00:02:45,000
+And now let me just compile this code once again.
+
+64
+00:02:45,000 --> 00:02:47,000
+So if you can see when I'm compiling it,
+
+65
+00:02:47,000 --> 00:02:50,000
+it is only compiling the Demo file.
+
+66
+00:02:50,000 --> 00:02:53,000
+It is not combining the class.java, right?
+
+67
+00:02:53,000 --> 00:02:55,000
+But when I create an object of it,
+
+68
+00:02:55,000 --> 00:02:58,000
+if I create object of Calc obj = new Calc,
+
+69
+00:02:58,000 --> 00:03:00,000
+of course if you want to use it,
+
+70
+00:03:00,000 --> 00:03:02,000
+we have to create object first.
+
+71
+00:03:02,000 --> 00:03:04,000
+And now if I recompile this,
+
+72
+00:03:04,000 --> 00:03:06,000
+and let's look at the class files.
+
+73
+00:03:06,000 --> 00:03:08,000
+We got the class file for class as well.
+
+74
+00:03:08,000 --> 00:03:12,000
+So if you are not using Calc, it will not compile it.
+
+75
+00:03:12,000 --> 00:03:13,000
+It'll just say, "Hey,
+
+76
+00:03:13,000 --> 00:03:15,000
+my responsibility is to compile the Java file.
+
+77
+00:03:15,000 --> 00:03:16,000
+I'm doing it."
+
+78
+00:03:16,000 --> 00:03:18,000
+But if you want to work with the class,
+
+79
+00:03:18,000 --> 00:03:21,000
+the Calc.class as well, or Calc.java as well,
+
+80
+00:03:21,000 --> 00:03:25,000
+you have to create object and that's how it compiles.
+
+81
+00:03:25,000 --> 00:03:26,000
+Now once the compile is done,
+
+82
+00:03:26,000 --> 00:03:30,000
+you can simply save the value in r1 or you can say obj.add.
+
+83
+00:03:30,000 --> 00:03:33,000
+It will add two numbers, let's say four and five.
+
+84
+00:03:33,000 --> 00:03:35,000
+And then we can also find r2,
+
+85
+00:03:35,000 --> 00:03:37,000
+which will be result of subtraction.
+
+86
+00:03:37,000 --> 00:03:41,000
+So I can say sub, I will say seven and three, okay?
+
+87
+00:03:41,000 --> 00:03:43,000
+So we basically, you can see we got these two methods,
+
+88
+00:03:43,000 --> 00:03:45,000
+and when you try to print the values,
+
+89
+00:03:45,000 --> 00:03:48,000
+I will print r1 and I will give us space,
+
+90
+00:03:48,000 --> 00:03:49,000
+and I'll also print r2.
+
+91
+00:03:49,000 --> 00:03:51,000
+So basically, I'm just printing two values back to back.
+
+92
+00:03:51,000 --> 00:03:55,000
+And if I say compile again because we have made some changes
+
+93
+00:03:55,000 --> 00:03:57,000
+and run, you can see we got nine and four.
+
+94
+00:03:57,000 --> 00:04:00,000
+So 4 + 5 is nine, 7 - 3 is four,
+
+95
+00:04:00,000 --> 00:04:02,000
+and that's what we are getting here.
+
+96
+00:04:02,000 --> 00:04:03,000
+Everything is working fine, right?
+
+97
+00:04:03,000 --> 00:04:05,000
+Now there are two conditions here,
+
+98
+00:04:05,000 --> 00:04:06,000
+why we are going for inheritance.
+
+99
+00:04:06,000 --> 00:04:09,000
+The first one is what if you want
+
+100
+00:04:09,000 --> 00:04:10,000
+to add some extra features?
+
+101
+00:04:10,000 --> 00:04:13,000
+You want, so let's say if someone is asking you for,
+
+102
+00:04:13,000 --> 00:04:14,000
+"Hey, you know, Navin,
+
+103
+00:04:14,000 --> 00:04:17,000
+I want a calculator and I want two features,
+
+104
+00:04:17,000 --> 00:04:19,000
+addition and subtraction.
+
+105
+00:04:19,000 --> 00:04:20,000
+What will be the cost?"
+
+106
+00:04:20,000 --> 00:04:22,000
+I would say, "Okay, I will charge you $10."
+
+107
+00:04:22,000 --> 00:04:24,000
+Now let's say the same person come back and say,
+
+108
+00:04:24,000 --> 00:04:27,000
+"Hey, you know, I want a calculator which has four features,
+
+109
+00:04:27,000 --> 00:04:29,000
+additional, subtraction, division, multiplication."
+
+110
+00:04:29,000 --> 00:04:33,000
+And maybe at this point, I want to charge $15.
+
+111
+00:04:33,000 --> 00:04:35,000
+Now of course, I can add those two methods here
+
+112
+00:04:35,000 --> 00:04:38,000
+or I can create a new class, you know why?
+
+113
+00:04:38,000 --> 00:04:41,000
+It's because if I edit the same file,
+
+114
+00:04:41,000 --> 00:04:42,000
+if I add more features here,
+
+115
+00:04:42,000 --> 00:04:45,000
+I can't sell calculator for $10 now.
+
+116
+00:04:45,000 --> 00:04:47,000
+I have to make a new product for $15.
+
+117
+00:04:47,000 --> 00:04:49,000
+I don't have calculator,
+
+118
+00:04:49,000 --> 00:04:51,000
+I have advanced calculator which does four operations.
+
+119
+00:04:51,000 --> 00:04:52,000
+I want both the models.
+
+120
+00:04:52,000 --> 00:04:57,000
+I want to sell the $10 calculator and a $15 calculator.
+
+121
+00:04:57,000 --> 00:04:59,000
+That's one reason. Okay, so let me just do that.
+
+122
+00:04:59,000 --> 00:05:01,000
+So let me create a new calculator,
+
+123
+00:05:01,000 --> 00:05:04,000
+and I will say this is advanced calculator,
+
+124
+00:05:04,000 --> 00:05:07,000
+which has all the features, .java.
+
+125
+00:05:07,000 --> 00:05:10,000
+And in this, I will basically have two more methods,
+
+126
+00:05:10,000 --> 00:05:15,000
+which is public int multi, which will take two values,
+
+127
+00:05:15,000 --> 00:05:19,000
+and it should return n1 into n2.
+
+128
+00:05:19,000 --> 00:05:21,000
+And likewise, we'll have one more method here for division.
+
+129
+00:05:21,000 --> 00:05:26,000
+So this is div and division, we have to say slash.
+
+130
+00:05:26,000 --> 00:05:28,000
+That's it, so we got an advanced calculator,
+
+131
+00:05:28,000 --> 00:05:29,000
+which has two features.
+
+132
+00:05:29,000 --> 00:05:33,000
+But now if I create an object of advanced calculator now,
+
+133
+00:05:33,000 --> 00:05:35,000
+instead of normal calculator,
+
+134
+00:05:35,000 --> 00:05:37,000
+I can access multiplication and division.
+
+135
+00:05:37,000 --> 00:05:39,000
+I can't access add and sub.
+
+136
+00:05:39,000 --> 00:05:41,000
+And that's why you can see we got an error here.
+
+137
+00:05:41,000 --> 00:05:44,000
+It says, "The method add is undefined
+
+138
+00:05:44,000 --> 00:05:46,000
+for type advanced calculator."
+
+139
+00:05:46,000 --> 00:05:48,000
+That means in this, we don't have add and subtract.
+
+140
+00:05:48,000 --> 00:05:50,000
+So what do you think? What could be solution here?
+
+141
+00:05:50,000 --> 00:05:52,000
+Think about this, so one solution,
+
+142
+00:05:52,000 --> 00:05:56,000
+which I can see is just write those two methods here.
+
+143
+00:05:56,000 --> 00:05:57,000
+Of course, we can do that.
+
+144
+00:05:57,000 --> 00:05:59,000
+Okay, we can just copy and we can paste it here.
+
+145
+00:05:59,000 --> 00:06:01,000
+But don't you think we are writing
+
+146
+00:06:01,000 --> 00:06:04,000
+the same code again and again?
+
+147
+00:06:04,000 --> 00:06:05,000
+Now when you repeat the same code,
+
+148
+00:06:05,000 --> 00:06:07,000
+it is called redundancy, right?
+
+149
+00:06:07,000 --> 00:06:12,000
+We have same code multiple times, and redundancy is a crime.
+
+150
+00:06:12,000 --> 00:06:13,000
+So make sure that you don't repeat the values,
+
+151
+00:06:13,000 --> 00:06:17,000
+you don't repeat the methods, definition, and classes.
+
+152
+00:06:17,000 --> 00:06:19,000
+The point is if I don't define it here,
+
+153
+00:06:19,000 --> 00:06:21,000
+how will I access them?
+
+154
+00:06:21,000 --> 00:06:24,000
+That's where the in inheritance concept comes into picture.
+
+155
+00:06:24,000 --> 00:06:26,000
+So in inheritance says, "Hey, don't worry.
+
+156
+00:06:26,000 --> 00:06:28,000
+If you already have a class called Calc,
+
+157
+00:06:28,000 --> 00:06:31,000
+you can simply say extends Calc, your job is done."
+
+158
+00:06:31,000 --> 00:06:34,000
+Okay, so you simply say advanced calculator
+
+159
+00:06:34,000 --> 00:06:37,000
+extends calculator, and now all the features
+
+160
+00:06:37,000 --> 00:06:40,000
+of calculator comes in here.
+
+161
+00:06:40,000 --> 00:06:41,000
+And there's one more beauty.
+
+162
+00:06:41,000 --> 00:06:44,000
+Even if you don't have this Java file, that's fine.
+
+163
+00:06:44,000 --> 00:06:48,000
+For inheritance, you need a class file, not a Java file.
+
+164
+00:06:48,000 --> 00:06:50,000
+So even if you delete this, it will still work, okay?
+
+165
+00:06:50,000 --> 00:06:51,000
+That's the first reason.
+
+166
+00:06:51,000 --> 00:06:53,000
+Even if you don't have a code ready with you,
+
+167
+00:06:53,000 --> 00:06:55,000
+even if you don't have a Java file,
+
+168
+00:06:55,000 --> 00:06:57,000
+you can still use a class file.
+
+169
+00:06:57,000 --> 00:06:59,000
+Okay, so that's the beauty of inheritance.
+
+170
+00:06:59,000 --> 00:07:01,000
+We are simply saying extends calculator,
+
+171
+00:07:01,000 --> 00:07:02,000
+which is this class.
+
+172
+00:07:02,000 --> 00:07:05,000
+Now what do you think, will it work? Let's try.
+
+173
+00:07:05,000 --> 00:07:06,000
+So you can see there's no problem,
+
+174
+00:07:06,000 --> 00:07:07,000
+add and subtraction working.
+
+175
+00:07:07,000 --> 00:07:09,000
+We can add some more variables here.
+
+176
+00:07:09,000 --> 00:07:13,000
+I can just copy this code and paste, paste,
+
+177
+00:07:13,000 --> 00:07:14,000
+not on the same line.
+
+178
+00:07:15,000 --> 00:07:18,000
+This is my r3, this is my r4,
+
+179
+00:07:18,000 --> 00:07:21,000
+and I can just say this is multiplication.
+
+180
+00:07:21,000 --> 00:07:23,000
+Okay, so multiplying number,
+
+181
+00:07:23,000 --> 00:07:27,000
+like let's say is five and three, okay?
+
+182
+00:07:27,000 --> 00:07:29,000
+And then dividing the number,
+
+183
+00:07:29,000 --> 00:07:33,000
+let's say 15 by 4.
+
+184
+00:07:33,000 --> 00:07:36,000
+Let's do this, and now when I perform this operation,
+
+185
+00:07:36,000 --> 00:07:39,000
+of course, I want to print r3 and r4 as well
+
+186
+00:07:39,000 --> 00:07:40,000
+on the same line.
+
+187
+00:07:40,000 --> 00:07:43,000
+I'm lazy to write multiple lines of code here, and r4.
+
+188
+00:07:43,000 --> 00:07:46,000
+So we are printing everything in the same line.
+
+189
+00:07:46,000 --> 00:07:48,000
+Let's try what happens.
+
+190
+00:07:48,000 --> 00:07:51,000
+Compile, no problem. Run, it works.
+
+191
+00:07:51,000 --> 00:07:54,000
+Can see that addition is nine, subtraction is four,
+
+192
+00:07:54,000 --> 00:07:56,000
+multiplication is 15, if I'm not wrong, yeah,
+
+193
+00:07:56,000 --> 00:07:58,000
+and division is three.
+
+194
+00:07:58,000 --> 00:08:02,000
+So 15 divided by four will give you a quotient of three.
+
+195
+00:08:02,000 --> 00:08:03,000
+Okay, cool, this is working right?
+
+196
+00:08:03,000 --> 00:08:06,000
+So this is how we use inheritance.
+
+197
+00:08:06,000 --> 00:08:10,000
+So important thing here is this advanced calculator
+
+198
+00:08:10,000 --> 00:08:11,000
+here is called a subclass.
+
+199
+00:08:11,000 --> 00:08:14,000
+This calculator here is called a superclass.
+
+200
+00:08:14,000 --> 00:08:18,000
+And to inherit, we use a keyword called extends, okay?
+
+201
+00:08:18,000 --> 00:08:22,000
+And this is basically a relationship of is-a.
+
+202
+00:08:22,000 --> 00:08:26,000
+Advanced calculator is a calculator,
+
+203
+00:08:26,000 --> 00:08:28,000
+and that's why we say is, an important word there.
+
+204
+00:08:28,000 --> 00:08:31,000
+Cool, can I have multiple classes in hitting each other?
+
+205
+00:08:31,000 --> 00:08:33,000
+We can, that's we'll see in the upcoming videos.
+
+206
+00:08:33,000 --> 00:08:36,000
+At this point, we just went for a simple inheritance
+
+207
+00:08:36,000 --> 00:08:39,000
+where we just use the feature of a superclass.
+
+208
+00:08:39,000 --> 00:08:41,000
+You can say parent has all these two features,
+
+209
+00:08:41,000 --> 00:08:44,000
+child is just extending it or using it.
+
+210
+00:08:44,000 --> 00:08:46,000
+I can say this is nepotism.
+
+211
+00:08:46,000 --> 00:08:47,000
+(laughs) So that's it from this video.
+
+212
+00:08:47,000 --> 00:08:50,000
+I hope you enjoyed and see you in the next video.
+
diff --git a/02 - Core Java/052 Need of Inheritance_en.srt b/02 - Core Java/052 Need of Inheritance_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..9ef9e3f5c50b2793ab0b43b98b44c161f17e2665
--- /dev/null
+++ b/02 - Core Java/052 Need of Inheritance_en.srt	
@@ -0,0 +1,664 @@
+1
+00:00:00,000 --> 00:00:03,000
+(bright music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: Now let's talk more about OOPs concept.
+
+3
+00:00:05,000 --> 00:00:09,000
+Now, OOPs basically stands for Object Oriented Programming.
+
+4
+00:00:09,000 --> 00:00:10,000
+Now, in Object Oriented Programming,
+
+5
+00:00:10,000 --> 00:00:14,000
+we have talked about Object Class Encapsulation, right?
+
+6
+00:00:14,000 --> 00:00:16,000
+Now let's talk more concepts.
+
+7
+00:00:16,000 --> 00:00:17,000
+Now, one of the most important thing
+
+8
+00:00:17,000 --> 00:00:21,000
+in the concept of OOPs is called inheritance.
+
+9
+00:00:21,000 --> 00:00:23,000
+Now, what is inheritance?
+
+10
+00:00:23,000 --> 00:00:25,000
+Now, there are two words actually here,
+
+11
+00:00:25,000 --> 00:00:30,000
+which will confuse people is, "is" and "has."
+
+12
+00:00:30,000 --> 00:00:32,000
+Now what these two words are.
+
+13
+00:00:32,000 --> 00:00:33,000
+Now, if we talk about a computer,
+
+14
+00:00:33,000 --> 00:00:36,000
+now, of course, computer itself is abstract concept, right?
+
+15
+00:00:36,000 --> 00:00:39,000
+Now a computer can be a laptop, a computer can be a desktop,
+
+16
+00:00:39,000 --> 00:00:41,000
+a computer can be a mobile phone.
+
+17
+00:00:41,000 --> 00:00:42,000
+That's right.
+
+18
+00:00:42,000 --> 00:00:43,000
+So even if you talk about this phone,
+
+19
+00:00:43,000 --> 00:00:47,000
+this is a computer in the form of mobile phone, of course.
+
+20
+00:00:47,000 --> 00:00:49,000
+And the computer itself is an abstract concept.
+
+21
+00:00:49,000 --> 00:00:50,000
+No one owns a computer.
+
+22
+00:00:50,000 --> 00:00:52,000
+You basically buy a hardware,
+
+23
+00:00:52,000 --> 00:00:54,000
+which can be a desktop, laptop, or a phone.
+
+24
+00:00:54,000 --> 00:00:57,000
+Now, can I say that if you talk about a desktop,
+
+25
+00:00:57,000 --> 00:00:58,000
+so I'm talking about a desktop, which is this big,
+
+26
+00:00:58,000 --> 00:01:01,000
+and it will have certain parts, right?
+
+27
+00:01:01,000 --> 00:01:02,000
+A desktop will have a motherboard,
+
+28
+00:01:02,000 --> 00:01:05,000
+a desktop will have a hard drive, CPU, ram.
+
+29
+00:01:05,000 --> 00:01:06,000
+So when you talk about this thing,
+
+30
+00:01:06,000 --> 00:01:10,000
+it is desktop has a motherboard,
+
+31
+00:01:10,000 --> 00:01:14,000
+desktop has a hard drive, it has a CPU, right?
+
+32
+00:01:14,000 --> 00:01:16,000
+So the important keyword there is "has."
+
+33
+00:01:16,000 --> 00:01:19,000
+If we talk about a house, a house will have a TV,
+
+34
+00:01:19,000 --> 00:01:22,000
+a house will have a sofa, AC, bed.
+
+35
+00:01:22,000 --> 00:01:25,000
+So all those things, what a house has, right?
+
+36
+00:01:25,000 --> 00:01:27,000
+So "has" is an important word.
+
+37
+00:01:27,000 --> 00:01:28,000
+But at this point, let's not focus on "has."
+
+38
+00:01:28,000 --> 00:01:30,000
+In this video, let's talk about "is."
+
+39
+00:01:30,000 --> 00:01:32,000
+Now what is, is, is.
+
+40
+00:01:32,000 --> 00:01:34,000
+Okay, so example, if we talk about a laptop,
+
+41
+00:01:34,000 --> 00:01:38,000
+so can we say a laptop is a computer?
+
+42
+00:01:38,000 --> 00:01:42,000
+So what it means is, laptop got it features from a computer.
+
+43
+00:01:42,000 --> 00:01:44,000
+So can we take another example here?
+
+44
+00:01:44,000 --> 00:01:46,000
+If we talk about a car, let's say.
+
+45
+00:01:46,000 --> 00:01:48,000
+Let's say if we talk about a Fortuner,
+
+46
+00:01:48,000 --> 00:01:49,000
+which is very famous in India.
+
+47
+00:01:49,000 --> 00:01:51,000
+So this car is actually a car, right?
+
+48
+00:01:51,000 --> 00:01:54,000
+So Fortuner is a car.
+
+49
+00:01:54,000 --> 00:01:55,000
+So that's how you represent something.
+
+50
+00:01:55,000 --> 00:01:58,000
+You represent a device or a physical entity
+
+51
+00:01:58,000 --> 00:02:00,000
+by referring to its upper model,
+
+52
+00:02:00,000 --> 00:02:02,000
+or you try to take the features of it.
+
+53
+00:02:02,000 --> 00:02:04,000
+Now, coming back to the Inheritance concept,
+
+54
+00:02:04,000 --> 00:02:06,000
+in real world example,
+
+55
+00:02:06,000 --> 00:02:08,000
+let's say if we talk about the human world,
+
+56
+00:02:08,000 --> 00:02:10,000
+you know, when I was in my 10th standard,
+
+57
+00:02:10,000 --> 00:02:12,000
+so just for the example, okay, not that important,
+
+58
+00:02:12,000 --> 00:02:16,000
+but when I was in my 10th standard, I did my 10th in 2005.
+
+59
+00:02:16,000 --> 00:02:20,000
+At that point, Nokia released a lot of smartphones, right?
+
+60
+00:02:20,000 --> 00:02:21,000
+Of course, Nokia is not there anymore,
+
+61
+00:02:21,000 --> 00:02:25,000
+but Nokia was one of the most important factor
+
+62
+00:02:25,000 --> 00:02:26,000
+in the smartphone industry.
+
+63
+00:02:26,000 --> 00:02:28,000
+Now, when they came up with a smartphone,
+
+64
+00:02:28,000 --> 00:02:31,000
+one of the most famous smartphone which they built is 6600.
+
+65
+00:02:31,000 --> 00:02:33,000
+I'm not sure if you have seen that.
+
+66
+00:02:33,000 --> 00:02:34,000
+I'm not even sure if you're that old.
+
+67
+00:02:34,000 --> 00:02:37,000
+Maybe you were not even born in that year.
+
+68
+00:02:37,000 --> 00:02:39,000
+But yeah, so it was 6600. Amazing phone.
+
+69
+00:02:39,000 --> 00:02:42,000
+If you can just search on Google, Nokia 6600,
+
+70
+00:02:42,000 --> 00:02:44,000
+you will see that phone.
+
+71
+00:02:44,000 --> 00:02:46,000
+Now, a lot of my friends were having that phone.
+
+72
+00:02:46,000 --> 00:02:47,000
+It was costly phone at that point.
+
+73
+00:02:47,000 --> 00:02:49,000
+It was around 10,000 rupees.
+
+74
+00:02:49,000 --> 00:02:51,000
+And I was not having any phone.
+
+75
+00:02:51,000 --> 00:02:52,000
+So they used to ask me, "Hey, which phone you have?"
+
+76
+00:02:52,000 --> 00:02:54,000
+I used to say, "Hey, I don't have a phone."
+
+77
+00:02:54,000 --> 00:02:58,000
+But then I realized, hey, till when I will say that.
+
+78
+00:02:58,000 --> 00:02:59,000
+The thing is,
+
+79
+00:02:59,000 --> 00:03:01,000
+next time when people used to ask me which phone I have,
+
+80
+00:03:01,000 --> 00:03:04,000
+I used to say I have 3310.
+
+81
+00:03:04,000 --> 00:03:05,000
+Now, I was not having any phone.
+
+82
+00:03:05,000 --> 00:03:07,000
+Now, this is my father's phone,
+
+83
+00:03:07,000 --> 00:03:09,000
+and we know the concept, right?
+
+84
+00:03:09,000 --> 00:03:10,000
+Father's phone is yours phone.
+
+85
+00:03:10,000 --> 00:03:12,000
+In fact, in general, we say,
+
+86
+00:03:12,000 --> 00:03:14,000
+our parents' property, it's your property.
+
+87
+00:03:14,000 --> 00:03:16,000
+Whatever they own, it's yours.
+
+88
+00:03:16,000 --> 00:03:17,000
+I don't believe in that, okay?
+
+89
+00:03:17,000 --> 00:03:20,000
+I'm not a big fan of inheritance or nepotism,
+
+90
+00:03:20,000 --> 00:03:22,000
+but yeah, you get everything.
+
+91
+00:03:22,000 --> 00:03:24,000
+So I used to say I have that phone.
+
+92
+00:03:24,000 --> 00:03:25,000
+Okay, so this is inheritance.
+
+93
+00:03:25,000 --> 00:03:27,000
+Now, how will you use this concept in programming?
+
+94
+00:03:27,000 --> 00:03:29,000
+Now in Java, what you have
+
+95
+00:03:29,000 --> 00:03:30,000
+is you have different classes, right?
+
+96
+00:03:30,000 --> 00:03:32,000
+Example, if you create a simple class here.
+
+97
+00:03:32,000 --> 00:03:33,000
+Let me get a very simple class.
+
+98
+00:03:33,000 --> 00:03:36,000
+Let's say we have a class here called Calculator.
+
+99
+00:03:36,000 --> 00:03:38,000
+Now what features a calculator will have?
+
+100
+00:03:38,000 --> 00:03:41,000
+A calculator will have some variables here,
+
+101
+00:03:41,000 --> 00:03:42,000
+and then it will have some methods.
+
+102
+00:03:42,000 --> 00:03:46,000
+Let's say method is add, a method is sub, okay?
+
+103
+00:03:46,000 --> 00:03:48,000
+And then method is multi.
+
+104
+00:03:48,000 --> 00:03:50,000
+So we have different methods here.
+
+105
+00:03:50,000 --> 00:03:51,000
+And let's also have division.
+
+106
+00:03:51,000 --> 00:03:53,000
+Why division should be left there?
+
+107
+00:03:53,000 --> 00:03:56,000
+So we have all these methods, right? And it is working.
+
+108
+00:03:56,000 --> 00:03:58,000
+So you can basically create object of Calculator,
+
+109
+00:03:58,000 --> 00:03:59,000
+and you can access all these methods.
+
+110
+00:03:59,000 --> 00:04:00,000
+No harm in that.
+
+111
+00:04:00,000 --> 00:04:04,000
+But what if you want to create a advanced calculator?
+
+112
+00:04:04,000 --> 00:04:06,000
+Now of course, let's say if someone comes to you
+
+113
+00:04:06,000 --> 00:04:09,000
+and say, "Hey, you know, you made a awesome calculator
+
+114
+00:04:09,000 --> 00:04:12,000
+and now I want you to create a scientific calculator
+
+115
+00:04:12,000 --> 00:04:14,000
+or advanced calculator."
+
+116
+00:04:14,000 --> 00:04:15,000
+Now you have a choice.
+
+117
+00:04:15,000 --> 00:04:18,000
+You can edit the same class, but there's only one thing.
+
+118
+00:04:18,000 --> 00:04:20,000
+What if you enhance the same class?
+
+119
+00:04:20,000 --> 00:04:21,000
+You add some more methods here.
+
+120
+00:04:21,000 --> 00:04:25,000
+Now you want to give Calculator to someone,
+
+121
+00:04:25,000 --> 00:04:27,000
+someone asking you for the Calculator object.
+
+122
+00:04:27,000 --> 00:04:28,000
+They basically access all the basic features
+
+123
+00:04:28,000 --> 00:04:30,000
+and advanced features, as well.
+
+124
+00:04:30,000 --> 00:04:33,000
+So it is good to create a separate class, okay?
+
+125
+00:04:33,000 --> 00:04:34,000
+So you can get a separate class,
+
+126
+00:04:34,000 --> 00:04:37,000
+and you can say Advanced Calculator, right?
+
+127
+00:04:37,000 --> 00:04:40,000
+And then this will have all the advanced features.
+
+128
+00:04:40,000 --> 00:04:41,000
+Of course, it will have all the basic features,
+
+129
+00:04:41,000 --> 00:04:43,000
+and it will have the advanced features, as well.
+
+130
+00:04:43,000 --> 00:04:46,000
+So we have basic features, advanced features both.
+
+131
+00:04:46,000 --> 00:04:47,000
+But don't you think
+
+132
+00:04:47,000 --> 00:04:51,000
+you need to define these basic features again and again?
+
+133
+00:04:51,000 --> 00:04:54,000
+Why? We already have those features here, right?
+
+134
+00:04:54,000 --> 00:04:56,000
+We already have those features here.
+
+135
+00:04:56,000 --> 00:05:01,000
+Can I just use those features in my new Advanced Calculator?
+
+136
+00:05:02,000 --> 00:05:04,000
+So what I'm saying is basically
+
+137
+00:05:04,000 --> 00:05:07,000
+this Advanced Calculator is going to inherit
+
+138
+00:05:07,000 --> 00:05:12,000
+the properties and features from Calculator.
+
+139
+00:05:12,000 --> 00:05:15,000
+So I can also say Advanced Calculator is a Calculator,
+
+140
+00:05:15,000 --> 00:05:17,000
+and it will get all the features of Calculator.
+
+141
+00:05:17,000 --> 00:05:20,000
+Okay, it will make much more sense once we start coding.
+
+142
+00:05:20,000 --> 00:05:24,000
+But what we are doing here is, we are doing inheritance.
+
+143
+00:05:24,000 --> 00:05:27,000
+So basically, inheritance is a very important feature,
+
+144
+00:05:27,000 --> 00:05:29,000
+using which you can just copy the feature
+
+145
+00:05:29,000 --> 00:05:31,000
+from the upper class.
+
+146
+00:05:31,000 --> 00:05:32,000
+Can I say this is a parent class?
+
+147
+00:05:32,000 --> 00:05:37,000
+So this is a parent class, and this is a child class
+
+148
+00:05:37,000 --> 00:05:39,000
+because child class is accessing
+
+149
+00:05:39,000 --> 00:05:41,000
+the feature of parent class, okay?
+
+150
+00:05:41,000 --> 00:05:44,000
+So whatever I earn, it's my money,
+
+151
+00:05:44,000 --> 00:05:45,000
+plus my parent's money is my money.
+
+152
+00:05:45,000 --> 00:05:46,000
+That's how the system works, right?
+
+153
+00:05:46,000 --> 00:05:49,000
+We can also say this is a super class.
+
+154
+00:05:49,000 --> 00:05:51,000
+We have different words for it. That's it.
+
+155
+00:05:51,000 --> 00:05:54,000
+And we can say this is a subclass.
+
+156
+00:05:54,000 --> 00:05:57,000
+We can also say this is a base class, base.
+
+157
+00:05:57,000 --> 00:06:00,000
+And this is a derived class.
+
+158
+00:06:00,000 --> 00:06:02,000
+So it depends upon how you represent that.
+
+159
+00:06:02,000 --> 00:06:04,000
+If you say this is a parent class,
+
+160
+00:06:04,000 --> 00:06:06,000
+then you have to say it's a child class.
+
+161
+00:06:06,000 --> 00:06:09,000
+If you say that's a super class, then it becomes a subclass.
+
+162
+00:06:09,000 --> 00:06:09,000
+If you say this is a base class,
+
+163
+00:06:09,000 --> 00:06:11,000
+you have to say this is a derived class.
+
+164
+00:06:11,000 --> 00:06:13,000
+That's how it works, okay?
+
+165
+00:06:13,000 --> 00:06:16,000
+Now, this is what inheritance is.
+
+166
+00:06:16,000 --> 00:06:19,000
+Now we'll try to implement this in code in the next video.
+
diff --git a/02 - Core Java/052 Source-code.url b/02 - Core Java/052 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/052 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/053 Single and Multilevel inheritance_en.srt b/02 - Core Java/053 Single and Multilevel inheritance_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..dd9ea35144928186d03647e650cb7e93fc926e39
--- /dev/null
+++ b/02 - Core Java/053 Single and Multilevel inheritance_en.srt	
@@ -0,0 +1,396 @@
+1
+00:00:00,000 --> 00:00:03,000
+(piano music opening)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: So basically we were able to do advanced calculator,
+
+3
+00:00:06,000 --> 00:00:08,000
+which uses a feature of calculator, right?
+
+4
+00:00:08,000 --> 00:00:10,000
+So this is extends.
+
+5
+00:00:10,000 --> 00:00:12,000
+Now what if in future,
+
+6
+00:00:12,000 --> 00:00:15,000
+let's say we got one more requirement, we want to build a,
+
+7
+00:00:15,000 --> 00:00:16,000
+let's say scientific calculator
+
+8
+00:00:16,000 --> 00:00:17,000
+and I don't know the operation,
+
+9
+00:00:17,000 --> 00:00:20,000
+so I will just say Very Advanced Calculator.
+
+10
+00:00:20,000 --> 00:00:23,000
+I'm very bad with names, so I will just use this
+
+11
+00:00:23,000 --> 00:00:26,000
+and this advanced calculator will have extra feature.
+
+12
+00:00:26,000 --> 00:00:27,000
+Let's say it also has a feature
+
+13
+00:00:27,000 --> 00:00:31,000
+of finding the power of a number.
+
+14
+00:00:31,000 --> 00:00:33,000
+Okay? So let's say public int,
+
+15
+00:00:33,000 --> 00:00:34,000
+I can simply say, yeah, power.
+
+16
+00:00:34,000 --> 00:00:37,000
+Now what we power, let's say three is two. I wanna do that.
+
+17
+00:00:37,000 --> 00:00:38,000
+So it'll take two numbers.
+
+18
+00:00:38,000 --> 00:00:40,000
+The first value N1,
+
+19
+00:00:40,000 --> 00:00:43,000
+and I also want a power, let's say N2
+
+20
+00:00:43,000 --> 00:00:44,000
+and let's say this will return, okay?
+
+21
+00:00:44,000 --> 00:00:47,000
+How do we do the power? So basically we have a math class.
+
+22
+00:00:47,000 --> 00:00:49,000
+I can just simply use it.
+
+23
+00:00:49,000 --> 00:00:52,000
+Math., yeah, we have a function of power.
+
+24
+00:00:52,000 --> 00:00:55,000
+Just take double value, but that's fine. I will just pass.
+
+25
+00:00:55,000 --> 00:00:57,000
+Integer double also takes integer value.
+
+26
+00:00:57,000 --> 00:00:58,000
+N1, N2.
+
+27
+00:00:58,000 --> 00:01:01,000
+And the problem is it also returns the double value.
+
+28
+00:01:01,000 --> 00:01:03,000
+If you can see, power returns are double value.
+
+29
+00:01:03,000 --> 00:01:06,000
+So what I will do is, let me return double value, okay?
+
+30
+00:01:06,000 --> 00:01:08,000
+So you have a choice, you can return double value
+
+31
+00:01:08,000 --> 00:01:12,000
+or you can just typecast it with int and you can do that.
+
+32
+00:01:12,000 --> 00:01:13,000
+Otherwise double is okay.
+
+33
+00:01:13,000 --> 00:01:14,000
+So you can see we have a power function,
+
+34
+00:01:14,000 --> 00:01:17,000
+which takes this method and it calculates.
+
+35
+00:01:17,000 --> 00:01:19,000
+Now the thing is, if I want to create
+
+36
+00:01:19,000 --> 00:01:21,000
+object of power, well I will do that.
+
+37
+00:01:21,000 --> 00:01:22,000
+I will just create that in demo.
+
+38
+00:01:22,000 --> 00:01:24,000
+I will say, hey, if someone wants
+
+39
+00:01:24,000 --> 00:01:28,000
+to try very advanced calculator, they can do that.
+
+40
+00:01:28,000 --> 00:01:30,000
+Okay? It is just that very advanced calculator.
+
+41
+00:01:30,000 --> 00:01:33,000
+If you can see, we don't have any of the methods. Okay?
+
+42
+00:01:33,000 --> 00:01:36,000
+Now that's an issue right?
+
+43
+00:01:36,000 --> 00:01:38,000
+Now I know in your mind you have a solution, right?
+
+44
+00:01:38,000 --> 00:01:40,000
+You have a choice. You can just add,
+
+45
+00:01:40,000 --> 00:01:42,000
+you can just type all these methods here
+
+46
+00:01:42,000 --> 00:01:46,000
+or we can come back here and say extends.
+
+47
+00:01:46,000 --> 00:01:47,000
+Okay? Now it'll extends what?.
+
+48
+00:01:47,000 --> 00:01:49,000
+We can also say calculator,
+
+49
+00:01:49,000 --> 00:01:52,000
+but then this will only have addition, subtraction,
+
+50
+00:01:52,000 --> 00:01:53,000
+division, multiplication,
+
+51
+00:01:53,000 --> 00:01:55,000
+but not the feature of advanced calculator,
+
+52
+00:01:55,000 --> 00:01:57,000
+which is, oh, it'll not have this two as well,
+
+53
+00:01:57,000 --> 00:02:00,000
+because this two is there in advanced calculator,
+
+54
+00:02:00,000 --> 00:02:01,000
+it'll only have add and sub.
+
+55
+00:02:01,000 --> 00:02:04,000
+You can see multi and division not found.
+
+56
+00:02:04,000 --> 00:02:05,000
+In fact, you know, I should also have R3.
+
+57
+00:02:05,000 --> 00:02:09,000
+In fact, this should be of type double, double R5 equal
+
+58
+00:02:09,000 --> 00:02:14,000
+to OBJ.power by passing two values.
+
+59
+00:02:14,000 --> 00:02:16,000
+One is, let's say four (indistinct),
+
+60
+00:02:16,000 --> 00:02:19,000
+at least we know the output should be 16.
+
+61
+00:02:19,000 --> 00:02:22,000
+And I also want to print R5.
+
+62
+00:02:22,000 --> 00:02:24,000
+Oh, we are printing everything in one line. Great.
+
+63
+00:02:24,000 --> 00:02:26,000
+And you can see multi and division are not working.
+
+64
+00:02:26,000 --> 00:02:28,000
+So if you want to make it work,
+
+65
+00:02:28,000 --> 00:02:29,000
+you can't just extends calculator, you have
+
+66
+00:02:29,000 --> 00:02:32,000
+to extends advanced calculator.
+
+67
+00:02:32,000 --> 00:02:34,000
+So you can see we have multiple hierarchy here.
+
+68
+00:02:34,000 --> 00:02:35,000
+So very advanced calculator is
+
+69
+00:02:35,000 --> 00:02:37,000
+extending advanced calculator.
+
+70
+00:02:37,000 --> 00:02:39,000
+Advanced calculator is extending calculator.
+
+71
+00:02:39,000 --> 00:02:42,000
+So if you try to compile this code, let's say if this works,
+
+72
+00:02:42,000 --> 00:02:45,000
+compile and run, you can see it's working.
+
+73
+00:02:45,000 --> 00:02:48,000
+You got 16 at the end, you got 0.0
+
+74
+00:02:48,000 --> 00:02:51,000
+because we are returning a double value.
+
+75
+00:02:51,000 --> 00:02:53,000
+This works. So if you're trying to imagine this,
+
+76
+00:02:53,000 --> 00:02:57,000
+what we are doing is, so we have a calculator
+
+77
+00:02:57,000 --> 00:03:00,000
+and then advanced calculator is extending calculator.
+
+78
+00:03:00,000 --> 00:03:04,000
+And then we got very advanced calculator is extending
+
+79
+00:03:04,000 --> 00:03:05,000
+from advanced calculator.
+
+80
+00:03:05,000 --> 00:03:08,000
+Now, this is when you are saying multiple,
+
+81
+00:03:08,000 --> 00:03:10,000
+where we are doing inheritance, right?
+
+82
+00:03:10,000 --> 00:03:14,000
+So this is called multilevel inheritance.
+
+83
+00:03:14,000 --> 00:03:17,000
+So basically we have multilevel inheritance here
+
+84
+00:03:17,000 --> 00:03:18,000
+because we have multiple level,
+
+85
+00:03:18,000 --> 00:03:22,000
+but in the early example we were having a just two, right?
+
+86
+00:03:22,000 --> 00:03:23,000
+So we were having this two.
+
+87
+00:03:23,000 --> 00:03:26,000
+Now when you say only two classes, this is called,
+
+88
+00:03:27,000 --> 00:03:30,000
+single level inheritance,
+
+89
+00:03:30,000 --> 00:03:32,000
+and I know I became a doctor there,
+
+90
+00:03:32,000 --> 00:03:34,000
+but you got the point, right?
+
+91
+00:03:34,000 --> 00:03:35,000
+So if you have multiple layers,
+
+92
+00:03:35,000 --> 00:03:37,000
+that is multi-level inheritance.
+
+93
+00:03:37,000 --> 00:03:39,000
+And when you say single, that is single,
+
+94
+00:03:39,000 --> 00:03:40,000
+when you have only two classes.
+
+95
+00:03:40,000 --> 00:03:44,000
+Now the very advanced calculator here is taking the feature
+
+96
+00:03:44,000 --> 00:03:45,000
+from advanced calculator.
+
+97
+00:03:45,000 --> 00:03:47,000
+Advanced calculator is taking the feature from calculator.
+
+98
+00:03:47,000 --> 00:03:50,000
+So by default, all the calc. stuff will come to
+
+99
+00:03:50,000 --> 00:03:52,000
+very advanced and that is multi-level.
+
diff --git a/02 - Core Java/053 Source-code.url b/02 - Core Java/053 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/053 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/054 Multiple Inheritance_en.srt b/02 - Core Java/054 Multiple Inheritance_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..603d0126f08cad19306cacb231143a2c27e50734
--- /dev/null
+++ b/02 - Core Java/054 Multiple Inheritance_en.srt	
@@ -0,0 +1,656 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle piano music)
+
+2
+00:00:03,000 --> 00:00:04,000
+-: So in the last video we have talked
+
+3
+00:00:04,000 --> 00:00:06,000
+about what is single level inheritance,
+
+4
+00:00:06,000 --> 00:00:08,000
+and then we have talked about multi-level, right?
+
+5
+00:00:08,000 --> 00:00:09,000
+Now what is multi-level?
+
+6
+00:00:09,000 --> 00:00:11,000
+So when you have the class,
+
+7
+00:00:11,000 --> 00:00:13,000
+which is getting inherited by someone else
+
+8
+00:00:13,000 --> 00:00:15,000
+and then something else is getting inherited
+
+9
+00:00:15,000 --> 00:00:16,000
+by something else.
+
+10
+00:00:16,000 --> 00:00:18,000
+It is multi-level.
+
+11
+00:00:18,000 --> 00:00:21,000
+Now, can we have a different structure here?
+
+12
+00:00:21,000 --> 00:00:22,000
+Let's take one more example.
+
+13
+00:00:22,000 --> 00:00:26,000
+So if you say we have A, we have B and we have C.
+
+14
+00:00:26,000 --> 00:00:28,000
+Now this is multi-level, right?
+
+15
+00:00:28,000 --> 00:00:31,000
+And of course when you have A and B, that's it.
+
+16
+00:00:31,000 --> 00:00:33,000
+This is single level.
+
+17
+00:00:33,000 --> 00:00:37,000
+But what if you have A and B, and then you have C,
+
+18
+00:00:37,000 --> 00:00:41,000
+where your A is your parent.
+
+19
+00:00:41,000 --> 00:00:42,000
+In fact, in this situation as well,
+
+20
+00:00:42,000 --> 00:00:44,000
+if you try to expand this one.
+
+21
+00:00:44,000 --> 00:00:49,000
+Here as well, we have this A as a parent,
+
+22
+00:00:50,000 --> 00:00:53,000
+and then this B becomes a child.
+
+23
+00:00:53,000 --> 00:00:55,000
+Now, B becomes child for A,
+
+24
+00:00:55,000 --> 00:00:59,000
+but then B is also a parent for C, right?
+
+25
+00:00:59,000 --> 00:01:00,000
+So C becomes child here.
+
+26
+00:01:00,000 --> 00:01:04,000
+Now, in the same way, if we talk about this A, B, C here.
+
+27
+00:01:04,000 --> 00:01:06,000
+We are saying both are parent,
+
+28
+00:01:06,000 --> 00:01:10,000
+so we have A as parent and B as parent,
+
+29
+00:01:10,000 --> 00:01:14,000
+and then C becomes a child.
+
+30
+00:01:14,000 --> 00:01:17,000
+So C is from A and B, both.
+
+31
+00:01:17,000 --> 00:01:19,000
+Now is it possible in Java?
+
+32
+00:01:19,000 --> 00:01:20,000
+Let's try.
+
+33
+00:01:20,000 --> 00:01:22,000
+In fact, it is possible in other language like C++.
+
+34
+00:01:22,000 --> 00:01:24,000
+Let's try in Java.
+
+35
+00:01:24,000 --> 00:01:26,000
+What I will do is I will just go back to the same class,
+
+36
+00:01:26,000 --> 00:01:28,000
+okay, same file, demo.
+
+37
+00:01:28,000 --> 00:01:30,000
+And here let me get a class called A.
+
+38
+00:01:30,000 --> 00:01:32,000
+And of course A will have some methods.
+
+39
+00:01:32,000 --> 00:01:34,000
+This should be capital A
+
+40
+00:01:34,000 --> 00:01:38,000
+and then class B and class C.
+
+41
+00:01:38,000 --> 00:01:42,000
+Okay, we have this three classes here, okay?
+
+42
+00:01:42,000 --> 00:01:46,000
+And let's say, okay, let's try this first.
+
+43
+00:01:46,000 --> 00:01:51,000
+If B extends from A and C extends from B, okay, this works.
+
+44
+00:01:54,000 --> 00:01:56,000
+We can see there's no problem here,
+
+45
+00:01:56,000 --> 00:02:01,000
+but what if I want the C to extends from A and B both.
+
+46
+00:02:01,000 --> 00:02:04,000
+As you can see, this syntax is not working.
+
+47
+00:02:04,000 --> 00:02:05,000
+It gives you an error as well.
+
+48
+00:02:05,000 --> 00:02:09,000
+You can't put a comma when you say extends A comma B, okay?
+
+49
+00:02:09,000 --> 00:02:12,000
+Does it means we can use extend B?
+
+50
+00:02:12,000 --> 00:02:13,000
+No, even this will not work.
+
+51
+00:02:13,000 --> 00:02:16,000
+So it doesn't matter what combination you do,
+
+52
+00:02:16,000 --> 00:02:20,000
+multiple inheritance in Java will not work.
+
+53
+00:02:20,000 --> 00:02:20,000
+Yeah.
+
+54
+00:02:20,000 --> 00:02:21,000
+So this thing will not work.
+
+55
+00:02:21,000 --> 00:02:24,000
+Multiple inheritance will not work.
+
+56
+00:02:24,000 --> 00:02:25,000
+But the question is why?
+
+57
+00:02:25,000 --> 00:02:27,000
+So let's try to understand that here.
+
+58
+00:02:27,000 --> 00:02:28,000
+Now, let's say if we go back
+
+59
+00:02:28,000 --> 00:02:30,000
+to this particular example here,
+
+60
+00:02:30,000 --> 00:02:33,000
+let's say you create object of B, okay?
+
+61
+00:02:33,000 --> 00:02:36,000
+In this scenario, if you create object of B, let's say obj.
+
+62
+00:02:36,000 --> 00:02:41,000
+Now, obj can call all the methods of B and A both.
+
+63
+00:02:41,000 --> 00:02:43,000
+So let's say in B, we have a method called show.
+
+64
+00:02:43,000 --> 00:02:45,000
+Okay, let's say there's a show method,
+
+65
+00:02:45,000 --> 00:02:49,000
+and then from obj, you are trying to call show.
+
+66
+00:02:49,000 --> 00:02:50,000
+Will this work?
+
+67
+00:02:50,000 --> 00:02:51,000
+Yes, this will work.
+
+68
+00:02:51,000 --> 00:02:55,000
+Let's say in A, we have a method called abc.
+
+69
+00:02:55,000 --> 00:02:59,000
+Now, if you try to call obj.abc, yes, this will work,
+
+70
+00:02:59,000 --> 00:03:02,000
+but what happens, you know when you say obj.abc,
+
+71
+00:03:02,000 --> 00:03:06,000
+it'll try to search for it first in the B class.
+
+72
+00:03:06,000 --> 00:03:07,000
+In B class, we don't have it.
+
+73
+00:03:07,000 --> 00:03:09,000
+So it'll say, okay, I don't have that method.
+
+74
+00:03:09,000 --> 00:03:11,000
+Maybe my parent class will have,
+
+75
+00:03:11,000 --> 00:03:13,000
+so it'll go to A by checking,
+
+76
+00:03:13,000 --> 00:03:14,000
+"Hey, do you have abc?"
+
+77
+00:03:14,000 --> 00:03:16,000
+Parent will say, "Yes, I have."
+
+78
+00:03:16,000 --> 00:03:18,000
+Now, in this case it'll work.
+
+79
+00:03:18,000 --> 00:03:20,000
+The same thing is applicable for C as well.
+
+80
+00:03:20,000 --> 00:03:23,000
+Let's say if you create object of C, which is obj again.
+
+81
+00:03:23,000 --> 00:03:26,000
+And then if you try to call a method,
+
+82
+00:03:26,000 --> 00:03:28,000
+let's say, A has a method called x,
+
+83
+00:03:28,000 --> 00:03:31,000
+B has a method called y and C has a method called z.
+
+84
+00:03:31,000 --> 00:03:33,000
+So let's say we have z method.
+
+85
+00:03:33,000 --> 00:03:35,000
+and then when you try to call z, this will work.
+
+86
+00:03:35,000 --> 00:03:37,000
+Because in C itself, we have the method.
+
+87
+00:03:37,000 --> 00:03:42,000
+If you say obj.y, will this work?
+
+88
+00:03:42,000 --> 00:03:44,000
+Yes, because it is coming from B.
+
+89
+00:03:44,000 --> 00:03:47,000
+Now, when you say obj.x,
+
+90
+00:03:47,000 --> 00:03:50,000
+it'll also work because it'll call from A.
+
+91
+00:03:50,000 --> 00:03:51,000
+So first it'll search in C.
+
+92
+00:03:51,000 --> 00:03:53,000
+In C, we don't have x, it'll go to B.
+
+93
+00:03:53,000 --> 00:03:55,000
+In B, also we don't have x.
+
+94
+00:03:55,000 --> 00:03:58,000
+It'll go to A, yes in A, we have x.
+
+95
+00:03:58,000 --> 00:04:00,000
+Okay, it works.
+
+96
+00:04:00,000 --> 00:04:02,000
+But now if you come back to this example,
+
+97
+00:04:02,000 --> 00:04:04,000
+let's say if you get object of C as obj.
+
+98
+00:04:04,000 --> 00:04:07,000
+So let's say this is C object, okay?
+
+99
+00:04:07,000 --> 00:04:10,000
+And then let's say in this A,
+
+100
+00:04:10,000 --> 00:04:12,000
+we have a method called show, okay?
+
+101
+00:04:12,000 --> 00:04:14,000
+And that's how we're working.
+
+102
+00:04:14,000 --> 00:04:17,000
+So let's say if you call show now,
+
+103
+00:04:17,000 --> 00:04:20,000
+now of course C will say, "Okay, I don't have a method show.
+
+104
+00:04:20,000 --> 00:04:22,000
+Will this work? Let me ask my parent."
+
+105
+00:04:22,000 --> 00:04:23,000
+So it'll go to A,
+
+106
+00:04:23,000 --> 00:04:26,000
+A will say, "Okay, I have show, problem solved."
+
+107
+00:04:26,000 --> 00:04:27,000
+This will work, right?
+
+108
+00:04:27,000 --> 00:04:28,000
+In general, I'm not talking about Java.
+
+109
+00:04:28,000 --> 00:04:30,000
+Let's say in general, this is how it works.
+
+110
+00:04:30,000 --> 00:04:34,000
+Now, let's say we have, in B, we have a method called X.
+
+111
+00:04:34,000 --> 00:04:35,000
+Okay?
+
+112
+00:04:35,000 --> 00:04:38,000
+Now it'll say obj.x, will this work?
+
+113
+00:04:38,000 --> 00:04:39,000
+Now it'll search and C.
+
+114
+00:04:39,000 --> 00:04:40,000
+In C, we don't have it.
+
+115
+00:04:40,000 --> 00:04:42,000
+In A, also we don't have it, in B we have it.
+
+116
+00:04:42,000 --> 00:04:44,000
+So this will also work.
+
+117
+00:04:44,000 --> 00:04:47,000
+Okay, but what if there's a method called y,
+
+118
+00:04:47,000 --> 00:04:51,000
+which is there in A and B, both, okay?
+
+119
+00:04:51,000 --> 00:04:55,000
+And now, if you're trying to say obj.y,
+
+120
+00:04:55,000 --> 00:04:59,000
+the problem is from C, we don't have it,
+
+121
+00:04:59,000 --> 00:05:03,000
+and A and B both has this method, which one he will choose?
+
+122
+00:05:03,000 --> 00:05:05,000
+That's a confusion, right?
+
+123
+00:05:05,000 --> 00:05:07,000
+It is almost same like let's say if you want
+
+124
+00:05:07,000 --> 00:05:09,000
+to call someone, your phone is dead,
+
+125
+00:05:09,000 --> 00:05:11,000
+and then now you want to call.
+
+126
+00:05:11,000 --> 00:05:12,000
+So you can ask your parents.
+
+127
+00:05:12,000 --> 00:05:13,000
+And both the parents has a phone,
+
+128
+00:05:13,000 --> 00:05:15,000
+which phone you will choose?
+
+129
+00:05:15,000 --> 00:05:18,000
+Now, if you chose your dad's phone,
+
+130
+00:05:18,000 --> 00:05:19,000
+your mom will feel bad.
+
+131
+00:05:19,000 --> 00:05:22,000
+If you choose your mom's phone, your dad will feel bad.
+
+132
+00:05:22,000 --> 00:05:25,000
+Again, I'm just giving an example here.
+
+133
+00:05:25,000 --> 00:05:26,000
+I'm not saying, it's literally happens,
+
+134
+00:05:26,000 --> 00:05:27,000
+but, in fact,
+
+135
+00:05:27,000 --> 00:05:29,000
+they'll be happy that you're not using their phone.
+
+136
+00:05:29,000 --> 00:05:32,000
+But yeah, that's a confusion we have here right now.
+
+137
+00:05:32,000 --> 00:05:36,000
+This problem is called ambiguity problem.
+
+138
+00:05:36,000 --> 00:05:37,000
+Okay?
+
+139
+00:05:37,000 --> 00:05:38,000
+So ambiguity simply means,
+
+140
+00:05:38,000 --> 00:05:40,000
+we have a confusion here, which one to choose?
+
+141
+00:05:40,000 --> 00:05:42,000
+Now, this problem is there in multiple languages,
+
+142
+00:05:42,000 --> 00:05:44,000
+which supports multiple inheritance.
+
+143
+00:05:44,000 --> 00:05:47,000
+Java says, "Oh, that's a problem?"
+
+144
+00:05:47,000 --> 00:05:49,000
+Let's remove the future itself.
+
+145
+00:05:49,000 --> 00:05:50,000
+Okay? I know.
+
+146
+00:05:50,000 --> 00:05:52,000
+That's a weird way of solving the problem,
+
+147
+00:05:52,000 --> 00:05:55,000
+but yeah, they have removed the problem itself.
+
+148
+00:05:55,000 --> 00:05:57,000
+So it's not like they found a solution.
+
+149
+00:05:57,000 --> 00:05:58,000
+They said,
+
+150
+00:05:58,000 --> 00:06:00,000
+"Instead of finding a solution, let's remove the feature."
+
+151
+00:06:00,000 --> 00:06:05,000
+That's right, in Java, multiple inheritance does not work.
+
+152
+00:06:05,000 --> 00:06:08,000
+Okay, so it's a very famous interview question,
+
+153
+00:06:08,000 --> 00:06:10,000
+do we support multiple inheritance in Java?
+
+154
+00:06:10,000 --> 00:06:11,000
+And the answer is no.
+
+155
+00:06:11,000 --> 00:06:13,000
+There is a internet way,
+
+156
+00:06:13,000 --> 00:06:15,000
+not actually a way,
+
+157
+00:06:15,000 --> 00:06:18,000
+just that it is possible by going all through steps.
+
+158
+00:06:18,000 --> 00:06:21,000
+But yeah, that's how Java is implemented in new feed,
+
+159
+00:06:21,000 --> 00:06:25,000
+in new versions, they have done something which changes it,
+
+160
+00:06:25,000 --> 00:06:26,000
+with the help of interfaces
+
+161
+00:06:26,000 --> 00:06:27,000
+but we don't know interfaces yet.
+
+162
+00:06:27,000 --> 00:06:32,000
+So, let's say, Java does not support multiple inheritance.
+
+163
+00:06:33,000 --> 00:06:35,000
+Oh, okay, this makes sense.
+
+164
+00:06:35,000 --> 00:06:36,000
+See you in the next video.
+
diff --git a/02 - Core Java/054 Source-code.url b/02 - Core Java/054 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/054 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/055 Source-code.url b/02 - Core Java/055 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/055 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/055 This and super method_en.srt b/02 - Core Java/055 This and super method_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..78d7da59bd4e4ff435375f509288de3dae3f3531
--- /dev/null
+++ b/02 - Core Java/055 This and super method_en.srt	
@@ -0,0 +1,1204 @@
+1
+00:00:00,000 --> 00:00:03,000
+(soft music plays)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, let's talk about this and super.
+
+3
+00:00:06,000 --> 00:00:09,000
+Now this is a very super concept, so let's focus, so
+
+4
+00:00:09,000 --> 00:00:10,000
+what I'll do is I'll just remove all this thing just
+
+5
+00:00:10,000 --> 00:00:13,000
+to make it simple and clear this part as well.
+
+6
+00:00:13,000 --> 00:00:18,000
+And for this, I don't even need this particular classes,
+
+7
+00:00:18,000 --> 00:00:21,000
+so let me just close these files and keep it simple.
+
+8
+00:00:21,000 --> 00:00:22,000
+Okay, so we have a very simple code here.
+
+9
+00:00:22,000 --> 00:00:25,000
+Now what I'll do is just to understand this
+
+10
+00:00:25,000 --> 00:00:28,000
+and Super, I will create a class called A,
+
+11
+00:00:28,000 --> 00:00:29,000
+I know this is a very simple name,
+
+12
+00:00:29,000 --> 00:00:32,000
+but just for the example we can take them
+
+13
+00:00:32,000 --> 00:00:34,000
+and then we got a class B.
+
+14
+00:00:34,000 --> 00:00:36,000
+Okay, we got two classes
+
+15
+00:00:36,000 --> 00:00:41,000
+and then I'm also saying that this B class extends A,
+
+16
+00:00:41,000 --> 00:00:44,000
+of course we are doing inheritance here and it makes sense
+
+17
+00:00:44,000 --> 00:00:46,000
+because we just talked about inheritance.
+
+18
+00:00:46,000 --> 00:00:48,000
+And then what I will do is I will create
+
+19
+00:00:48,000 --> 00:00:49,000
+a constructor for both.
+
+20
+00:00:49,000 --> 00:00:51,000
+Of course we can do that, right?
+
+21
+00:00:51,000 --> 00:00:53,000
+Now before creating a constructor,
+
+22
+00:00:53,000 --> 00:00:55,000
+let me say if I create object of B,
+
+23
+00:00:55,000 --> 00:00:57,000
+of course we can do that, right?
+
+24
+00:00:57,000 --> 00:01:00,000
+So this B class, we got an object of B class here
+
+25
+00:01:00,000 --> 00:01:01,000
+and we can do that.
+
+26
+00:01:01,000 --> 00:01:04,000
+Let me create a constructor of B here.
+
+27
+00:01:04,000 --> 00:01:06,000
+Now how do we create a constructor? It's very simple.
+
+28
+00:01:06,000 --> 00:01:09,000
+You specify public and then you say B, bracket open,
+
+29
+00:01:09,000 --> 00:01:13,000
+and then here I will type in B.
+
+30
+00:01:13,000 --> 00:01:14,000
+I'm just trying to keep it as simple as possible.
+
+31
+00:01:14,000 --> 00:01:16,000
+That's why we have taken class A and B
+
+32
+00:01:16,000 --> 00:01:18,000
+and then a very simple statement.
+
+33
+00:01:18,000 --> 00:01:20,000
+Now what I will do is I will try to compile this code
+
+34
+00:01:20,000 --> 00:01:22,000
+and you tell me what will be the output.
+
+35
+00:01:22,000 --> 00:01:23,000
+Compression done, right?
+
+36
+00:01:23,000 --> 00:01:26,000
+If I run this code, there will be some output. Right?
+
+37
+00:01:26,000 --> 00:01:28,000
+Now think about this: We are creating the object of B.
+
+38
+00:01:28,000 --> 00:01:32,000
+We are instantiating it and we have learned about this that
+
+39
+00:01:32,000 --> 00:01:33,000
+whenever you create the object,
+
+40
+00:01:33,000 --> 00:01:35,000
+it'll call the constructor of a class.
+
+41
+00:01:35,000 --> 00:01:37,000
+So the object we are getting is of B,
+
+42
+00:01:37,000 --> 00:01:40,000
+and we have a constructor, which is B here,
+
+43
+00:01:40,000 --> 00:01:42,000
+which prints a statement.
+
+44
+00:01:42,000 --> 00:01:43,000
+So of course I'm expecting
+
+45
+00:01:43,000 --> 00:01:46,000
+that it'll execute the constructor and it will.
+
+46
+00:01:46,000 --> 00:01:48,000
+That's what you got in B.
+
+47
+00:01:48,000 --> 00:01:49,000
+That perfectly makes sense and we have talked
+
+48
+00:01:49,000 --> 00:01:50,000
+about this from a long time.
+
+49
+00:01:50,000 --> 00:01:54,000
+The twist here is, what if I have a constructor
+
+50
+00:01:54,000 --> 00:01:56,000
+in A as well?
+
+51
+00:01:56,000 --> 00:01:59,000
+And here I'm printing in A.
+
+52
+00:01:59,000 --> 00:02:01,000
+Now what do you think will be the output?
+
+53
+00:02:01,000 --> 00:02:05,000
+Because of course we are grading the object of B, not A,
+
+54
+00:02:05,000 --> 00:02:09,000
+so it should call the constructor of B and that makes sense.
+
+55
+00:02:09,000 --> 00:02:10,000
+But if you compile this code,
+
+56
+00:02:10,000 --> 00:02:12,000
+you will see something strange.
+
+57
+00:02:12,000 --> 00:02:13,000
+If I compile this code
+
+58
+00:02:13,000 --> 00:02:17,000
+and run, oh, it is also executing the constructor of A.
+
+59
+00:02:17,000 --> 00:02:19,000
+Now that's weird for us, right?
+
+60
+00:02:19,000 --> 00:02:22,000
+Because we are creating object of B,
+
+61
+00:02:22,000 --> 00:02:24,000
+it should only call the construct of B,
+
+62
+00:02:24,000 --> 00:02:26,000
+but it is also calling the construct of A,
+
+63
+00:02:26,000 --> 00:02:28,000
+and that sounds weird.
+
+64
+00:02:28,000 --> 00:02:31,000
+Now we understand that, but at this point, just remember
+
+65
+00:02:31,000 --> 00:02:32,000
+whenever you get object of a class,
+
+66
+00:02:32,000 --> 00:02:36,000
+it'll call the constructor of subclass and superclass both.
+
+67
+00:02:36,000 --> 00:02:39,000
+A is a superclass here, B is subclass.
+
+68
+00:02:39,000 --> 00:02:41,000
+It'll call the constructor of both.
+
+69
+00:02:41,000 --> 00:02:43,000
+Why? We'll talk about it in some time,
+
+70
+00:02:43,000 --> 00:02:45,000
+but it calls the constructor of both.
+
+71
+00:02:45,000 --> 00:02:46,000
+Now let me just add a twist here,
+
+72
+00:02:46,000 --> 00:02:50,000
+in B, let me create a parameterize constructor,
+
+73
+00:02:50,000 --> 00:02:51,000
+and we have seen that, right?
+
+74
+00:02:51,000 --> 00:02:53,000
+So what is parameterize constructor?
+
+75
+00:02:53,000 --> 00:02:55,000
+A constructor which takes a value.
+
+76
+00:02:55,000 --> 00:02:56,000
+Let's say this is N, okay?
+
+77
+00:02:56,000 --> 00:03:00,000
+And here, I'll print "in B int"
+
+78
+00:03:00,000 --> 00:03:03,000
+because we have a constructor which takes
+
+79
+00:03:03,000 --> 00:03:04,000
+a int n parameter.
+
+80
+00:03:04,000 --> 00:03:07,000
+I'm just printing just int just to differentiate
+
+81
+00:03:07,000 --> 00:03:08,000
+between these two statements.
+
+82
+00:03:08,000 --> 00:03:11,000
+Now with this, if I compile this code and run,
+
+83
+00:03:11,000 --> 00:03:11,000
+what do you think?
+
+84
+00:03:11,000 --> 00:03:13,000
+What will be the output?
+
+85
+00:03:13,000 --> 00:03:14,000
+Compile and run.
+
+86
+00:03:14,000 --> 00:03:16,000
+Still it is in A and in B.
+
+87
+00:03:16,000 --> 00:03:18,000
+Why not in B int is because
+
+88
+00:03:18,000 --> 00:03:20,000
+when you are creating the object,
+
+89
+00:03:20,000 --> 00:03:22,000
+you are not passing any value here.
+
+90
+00:03:22,000 --> 00:03:25,000
+Basically you are calling a default constructor,
+
+91
+00:03:25,000 --> 00:03:27,000
+but if you pass a value, let's say five,
+
+92
+00:03:27,000 --> 00:03:30,000
+in this case you are specifically mentioning, "Hey,
+
+93
+00:03:30,000 --> 00:03:32,000
+I'm creating an object of B
+
+94
+00:03:32,000 --> 00:03:34,000
+and I'm passing a integer here,
+
+95
+00:03:34,000 --> 00:03:38,000
+so it'll call the constructor of B, which takes integer.
+
+96
+00:03:38,000 --> 00:03:41,000
+Now by doing this, if I run this code,
+
+97
+00:03:41,000 --> 00:03:43,000
+or you can see it is printing in A
+
+98
+00:03:43,000 --> 00:03:45,000
+and in B, int.
+
+99
+00:03:45,000 --> 00:03:47,000
+Okay, that actually makes sense.
+
+100
+00:03:47,000 --> 00:03:49,000
+It'll call the construct of A,
+
+101
+00:03:49,000 --> 00:03:53,000
+but what if I also have a parameterize constructor in
+
+102
+00:03:53,000 --> 00:03:55,000
+A as well, which takes a N
+
+103
+00:03:55,000 --> 00:03:59,000
+and it also prints in A int.
+
+104
+00:03:59,000 --> 00:04:02,000
+Now, since we were not having a parameterize constructor,
+
+105
+00:04:02,000 --> 00:04:03,000
+it was called a (indistinct) constructor.
+
+106
+00:04:03,000 --> 00:04:05,000
+That's what I'm assuming at this point.
+
+107
+00:04:05,000 --> 00:04:08,000
+Now, when you have a parameterize constructor for both,
+
+108
+00:04:08,000 --> 00:04:10,000
+for A and B both,
+
+109
+00:04:10,000 --> 00:04:12,000
+now there is an expectation
+
+110
+00:04:12,000 --> 00:04:15,000
+that it'll print in A int and in B int.
+
+111
+00:04:15,000 --> 00:04:16,000
+And that's what I'm thinking.
+
+112
+00:04:16,000 --> 00:04:18,000
+I'm not sure what you are thinking.
+
+113
+00:04:18,000 --> 00:04:20,000
+Let's try, let's see if this works.
+
+114
+00:04:20,000 --> 00:04:23,000
+Oh no, what is happening here?
+
+115
+00:04:23,000 --> 00:04:26,000
+It is calling the the parameters constructor of B.
+
+116
+00:04:26,000 --> 00:04:27,000
+That actually makes sense, but why?
+
+117
+00:04:27,000 --> 00:04:29,000
+The default construct of A,
+
+118
+00:04:29,000 --> 00:04:32,000
+it should have been called this one, right?
+
+119
+00:04:32,000 --> 00:04:34,000
+Let's understand why it is first of all,
+
+120
+00:04:34,000 --> 00:04:36,000
+calling the constructor of parent class.
+
+121
+00:04:36,000 --> 00:04:37,000
+Why in the first place?
+
+122
+00:04:37,000 --> 00:04:40,000
+The thing is, and remember this point,
+
+123
+00:04:40,000 --> 00:04:45,000
+every constructor in Java has a method which is there,
+
+124
+00:04:47,000 --> 00:04:49,000
+even if you don't mention, okay?
+
+125
+00:04:49,000 --> 00:04:52,000
+And that method is super.
+
+126
+00:04:52,000 --> 00:04:56,000
+Now this method is there, even if you don't mention,
+
+127
+00:04:56,000 --> 00:04:57,000
+you can imagine that's like a John Cena.
+
+128
+00:04:57,000 --> 00:04:59,000
+I don't know if you know the John Cena memes.
+
+129
+00:04:59,000 --> 00:05:02,000
+It's just that you can't see it. Okay?
+
+130
+00:05:02,000 --> 00:05:03,000
+So super is there. You can't see it.
+
+131
+00:05:03,000 --> 00:05:06,000
+Even if you don't mention super, it is there.
+
+132
+00:05:06,000 --> 00:05:08,000
+So by default, every constructor,
+
+133
+00:05:08,000 --> 00:05:11,000
+the first statement is super
+
+134
+00:05:11,000 --> 00:05:14,000
+and every constructor not just this one,
+
+135
+00:05:14,000 --> 00:05:16,000
+every constructor, here as well.
+
+136
+00:05:16,000 --> 00:05:17,000
+Super, okay?
+
+137
+00:05:17,000 --> 00:05:20,000
+So every constructor will have super.
+
+138
+00:05:20,000 --> 00:05:22,000
+Same goes for A as well.
+
+139
+00:05:22,000 --> 00:05:23,000
+It'll also have super
+
+140
+00:05:24,000 --> 00:05:26,000
+and super,
+
+141
+00:05:26,000 --> 00:05:27,000
+irrespective to which class it is.
+
+142
+00:05:27,000 --> 00:05:29,000
+It'll have this statement super,
+
+143
+00:05:29,000 --> 00:05:31,000
+even if you don't mention it, is there, okay?
+
+144
+00:05:31,000 --> 00:05:32,000
+That's a point to remember.
+
+145
+00:05:32,000 --> 00:05:35,000
+Now let's try to understand how it is working.
+
+146
+00:05:35,000 --> 00:05:36,000
+Let's do a dry run.
+
+147
+00:05:36,000 --> 00:05:39,000
+The moment you execute this statement, what is happening?
+
+148
+00:05:39,000 --> 00:05:43,000
+It is calling the constructor of B, which is parametrized.
+
+149
+00:05:43,000 --> 00:05:46,000
+So it is calling this program method.
+
+150
+00:05:46,000 --> 00:05:47,000
+So when you execute this method,
+
+151
+00:05:47,000 --> 00:05:52,000
+the first thing it sees is super, not the system.println
+
+152
+00:05:52,000 --> 00:05:54,000
+What it is saying is super. Now what is super?
+
+153
+00:05:54,000 --> 00:05:57,000
+Now super method simply means call the constructor
+
+154
+00:05:57,000 --> 00:05:59,000
+of a super class.
+
+155
+00:05:59,000 --> 00:06:00,000
+So let me repeat.
+
+156
+00:06:00,000 --> 00:06:05,000
+Super means: call the constructor of a super class.
+
+157
+00:06:05,000 --> 00:06:07,000
+Now what's the in super class?
+
+158
+00:06:07,000 --> 00:06:10,000
+This is a super class, it is calling the constructor
+
+159
+00:06:10,000 --> 00:06:12,000
+of a super class, but which one?
+
+160
+00:06:12,000 --> 00:06:14,000
+The parameterized one.
+
+161
+00:06:14,000 --> 00:06:18,000
+So the default one, if you can see we are saying default,
+
+162
+00:06:18,000 --> 00:06:20,000
+we are not passing any parameter here.
+
+163
+00:06:20,000 --> 00:06:24,000
+So it is calling this particular constructor
+
+164
+00:06:24,000 --> 00:06:27,000
+and that's why it's printing in A,
+
+165
+00:06:27,000 --> 00:06:29,000
+and that's why if you can see the output,
+
+166
+00:06:29,000 --> 00:06:30,000
+it is first printing in A,
+
+167
+00:06:30,000 --> 00:06:34,000
+and then once it executes the A constructor,
+
+168
+00:06:34,000 --> 00:06:37,000
+it'll execute the remaining part of B constructor,
+
+169
+00:06:37,000 --> 00:06:40,000
+which is this part, in B int.
+
+170
+00:06:40,000 --> 00:06:42,000
+And that's why we got in B int, okay?
+
+171
+00:06:42,000 --> 00:06:46,000
+That means, if I don't want to call this constructor,
+
+172
+00:06:46,000 --> 00:06:49,000
+if I want to call the parameterized one, we have
+
+173
+00:06:49,000 --> 00:06:51,000
+to do only one change, which is
+
+174
+00:06:51,000 --> 00:06:55,000
+what if in this super you pass a number?
+
+175
+00:06:55,000 --> 00:06:57,000
+So any is a value, right? It'll have a value,
+
+176
+00:06:57,000 --> 00:07:00,000
+the same value you are passing to this super.
+
+177
+00:07:00,000 --> 00:07:02,000
+Now what we are saying is, "Hey Java, I know
+
+178
+00:07:02,000 --> 00:07:05,000
+you are going to execute this super class constructor,
+
+179
+00:07:05,000 --> 00:07:06,000
+but I'm passing a parameter there."
+
+180
+00:07:06,000 --> 00:07:08,000
+So now this time you have to call
+
+181
+00:07:08,000 --> 00:07:10,000
+the parameterized constructor.
+
+182
+00:07:10,000 --> 00:07:13,000
+By doing those changes, let's compile and run.
+
+183
+00:07:13,000 --> 00:07:14,000
+Here we go.
+
+184
+00:07:14,000 --> 00:07:17,000
+It is printing in A int and in B int.
+
+185
+00:07:17,000 --> 00:07:20,000
+So super is a very handy tool. It's there already.
+
+186
+00:07:20,000 --> 00:07:21,000
+You don't have to mention that,
+
+187
+00:07:21,000 --> 00:07:23,000
+but if you want to make some changes, of course you will
+
+188
+00:07:23,000 --> 00:07:24,000
+but you have to mention.
+
+189
+00:07:24,000 --> 00:07:26,000
+So if you want to pass a parametrized constructor,
+
+190
+00:07:26,000 --> 00:07:30,000
+then explicitly you have to mention super.
+
+191
+00:07:30,000 --> 00:07:33,000
+I hope that made some sense. Okay?
+
+192
+00:07:33,000 --> 00:07:35,000
+Now what I want is, I want to call
+
+193
+00:07:35,000 --> 00:07:38,000
+the default constructor of B.
+
+194
+00:07:38,000 --> 00:07:40,000
+Okay? I'm not passing any parameter here.
+
+195
+00:07:40,000 --> 00:07:42,000
+I'm calling a object of B.
+
+196
+00:07:42,000 --> 00:07:46,000
+So of course if I execute this, if I compile and run,
+
+197
+00:07:46,000 --> 00:07:49,000
+you can see it's printing in A and in B.
+
+198
+00:07:49,000 --> 00:07:50,000
+Why?
+
+199
+00:07:50,000 --> 00:07:52,000
+It's because when you are calling
+
+200
+00:07:52,000 --> 00:07:55,000
+the default constructor here in default construct of B,
+
+201
+00:07:55,000 --> 00:07:56,000
+it'll execute first.
+
+202
+00:07:56,000 --> 00:07:58,000
+It is calling this super,
+
+203
+00:07:58,000 --> 00:08:00,000
+that means it is calling this part constructor,
+
+204
+00:08:00,000 --> 00:08:05,000
+which is printing in A, and then it is printing in B.
+
+205
+00:08:05,000 --> 00:08:08,000
+It'll continue with this execution of B, right?
+
+206
+00:08:08,000 --> 00:08:11,000
+But what I want now is I know you got the point,
+
+207
+00:08:11,000 --> 00:08:14,000
+what I want is I want to execute in A int
+
+208
+00:08:14,000 --> 00:08:18,000
+and then I want to print in B.
+
+209
+00:08:18,000 --> 00:08:21,000
+So the output which I want is, in A INT in B.
+
+210
+00:08:21,000 --> 00:08:23,000
+So how can we play with that?
+
+211
+00:08:23,000 --> 00:08:26,000
+So what if here, if I pass a value at say five
+
+212
+00:08:26,000 --> 00:08:27,000
+or any number, doesn't matter.
+
+213
+00:08:27,000 --> 00:08:30,000
+If I pass a number, it'll try to create object of B
+
+214
+00:08:30,000 --> 00:08:31,000
+with a default constructor,
+
+215
+00:08:31,000 --> 00:08:33,000
+it'll execute a default constructor.
+
+216
+00:08:33,000 --> 00:08:36,000
+But now we are calling a super class constructor
+
+217
+00:08:36,000 --> 00:08:38,000
+by passing a value.
+
+218
+00:08:38,000 --> 00:08:41,000
+So which constructor will be called?
+
+219
+00:08:41,000 --> 00:08:46,000
+Of course the second one and it'll print in A int in B.
+
+220
+00:08:46,000 --> 00:08:49,000
+Let's try, compile, run.
+
+221
+00:08:49,000 --> 00:08:50,000
+And that's what we got.
+
+222
+00:08:50,000 --> 00:08:54,000
+So that's how we can play with super and that is fun. Right?
+
+223
+00:08:54,000 --> 00:08:55,000
+Now I have a question for you.
+
+224
+00:08:55,000 --> 00:08:57,000
+Maybe you have observed it or not.
+
+225
+00:08:57,000 --> 00:08:59,000
+See in B class, when we are saying super,
+
+226
+00:08:59,000 --> 00:09:02,000
+it actually makes sense because we have a super class for B.
+
+227
+00:09:02,000 --> 00:09:05,000
+Okay? This is A here is a super class.
+
+228
+00:09:05,000 --> 00:09:08,000
+But when you say super for A, what is a super class for A?
+
+229
+00:09:08,000 --> 00:09:10,000
+We have not mentioned anything here, right?
+
+230
+00:09:10,000 --> 00:09:12,000
+Okay, now that's why we have to introduce
+
+231
+00:09:12,000 --> 00:09:13,000
+a new concept here.
+
+232
+00:09:13,000 --> 00:09:16,000
+Every class in Java, let me repeat.
+
+233
+00:09:16,000 --> 00:09:21,000
+Every class in Java extends the object class.
+
+234
+00:09:22,000 --> 00:09:27,000
+So object is a class in Java, which has a lot of methods.
+
+235
+00:09:27,000 --> 00:09:28,000
+We'll talk about those methods later.
+
+236
+00:09:28,000 --> 00:09:32,000
+But every class in Java extends this class.
+
+237
+00:09:32,000 --> 00:09:34,000
+Even if you don't mention, so even
+
+238
+00:09:34,000 --> 00:09:36,000
+if you don't mention this, it is extending it.
+
+239
+00:09:36,000 --> 00:09:39,000
+Again, you can imagine this as a John Cena,
+
+240
+00:09:39,000 --> 00:09:40,000
+it's there, you can't see it.
+
+241
+00:09:40,000 --> 00:09:43,000
+Okay? So even if you don't mention, or you mention,
+
+242
+00:09:43,000 --> 00:09:44,000
+it's the same thing.
+
+243
+00:09:44,000 --> 00:09:46,000
+So when you say super here,
+
+244
+00:09:46,000 --> 00:09:50,000
+you're basically calling a constructor of the object class.
+
+245
+00:09:50,000 --> 00:09:53,000
+Okay? In object class, also we have a constructor.
+
+246
+00:09:53,000 --> 00:09:56,000
+This is what you are calling, cool, right?
+
+247
+00:09:56,000 --> 00:09:58,000
+So even if you don't mention it, it's there.
+
+248
+00:09:58,000 --> 00:10:01,000
+Now you might be thinking the B class must be
+
+249
+00:10:01,000 --> 00:10:02,000
+extending A and object both?
+
+250
+00:10:02,000 --> 00:10:06,000
+No, B class extends A, A class extends objects.
+
+251
+00:10:06,000 --> 00:10:08,000
+So this is multi-level inheritance, okay?
+
+252
+00:10:08,000 --> 00:10:10,000
+There's no multiples till now, okay?
+
+253
+00:10:10,000 --> 00:10:13,000
+So yeah, that's how it works. We have object class.
+
+254
+00:10:13,000 --> 00:10:16,000
+So this super represents the constructor
+
+255
+00:10:16,000 --> 00:10:17,000
+of the object class.
+
+256
+00:10:17,000 --> 00:10:20,000
+So we have talked about super, but what is this?
+
+257
+00:10:20,000 --> 00:10:22,000
+Okay, now let me introduce this here.
+
+258
+00:10:22,000 --> 00:10:25,000
+The output, which I want now is, I want to execute
+
+259
+00:10:25,000 --> 00:10:28,000
+both the constructor of B.
+
+260
+00:10:28,000 --> 00:10:29,000
+Okay? So let me just keep it default now,
+
+261
+00:10:29,000 --> 00:10:30,000
+let me say super,
+
+262
+00:10:30,000 --> 00:10:33,000
+I want to execute both the constructor of B.
+
+263
+00:10:33,000 --> 00:10:35,000
+So I want only one object, okay?
+
+264
+00:10:35,000 --> 00:10:38,000
+With one object, can I execute both the constructor?
+
+265
+00:10:38,000 --> 00:10:40,000
+Of course I want to execute the constructor of A,
+
+266
+00:10:40,000 --> 00:10:44,000
+which is default, but I want to execute the constructor
+
+267
+00:10:44,000 --> 00:10:46,000
+of both B.
+
+268
+00:10:46,000 --> 00:10:50,000
+So what I'm saying is, I want in A, I want in B
+
+269
+00:10:50,000 --> 00:10:53,000
+and in B int, is it possible?
+
+270
+00:10:53,000 --> 00:10:55,000
+For that, what we can do is,
+
+271
+00:10:55,000 --> 00:10:57,000
+see we are creating the constructor.
+
+272
+00:10:57,000 --> 00:11:00,000
+Let me pass a value here, let me pass five.
+
+273
+00:11:00,000 --> 00:11:01,000
+So of course by doing that,
+
+274
+00:11:01,000 --> 00:11:03,000
+what we are doing is we are calling the constructor,
+
+275
+00:11:03,000 --> 00:11:06,000
+which is the parametized one, and we are calling super
+
+276
+00:11:06,000 --> 00:11:09,000
+and that's what's calling the super class constructor.
+
+277
+00:11:09,000 --> 00:11:11,000
+But then we have one more method called this.
+
+278
+00:11:11,000 --> 00:11:13,000
+We have talked about this keyword, right?
+
+279
+00:11:13,000 --> 00:11:15,000
+Now, what this will do is,
+
+280
+00:11:15,000 --> 00:11:18,000
+this will execute the construct of a same class.
+
+281
+00:11:18,000 --> 00:11:19,000
+Let me repeat:
+
+282
+00:11:19,000 --> 00:11:23,000
+This will execute the constructor of a same class,
+
+283
+00:11:23,000 --> 00:11:24,000
+which is this one.
+
+284
+00:11:24,000 --> 00:11:26,000
+We are not passing in a parameter.
+
+285
+00:11:26,000 --> 00:11:29,000
+So it'll call the construct of a same class.
+
+286
+00:11:29,000 --> 00:11:32,000
+And then this constructor is calling the construct
+
+287
+00:11:32,000 --> 00:11:32,000
+of a super class.
+
+288
+00:11:32,000 --> 00:11:36,000
+Let's try this works, compile, run.
+
+289
+00:11:36,000 --> 00:11:40,000
+And you can see that we got in A, in B, in B int.
+
+290
+00:11:40,000 --> 00:11:43,000
+I mean of course this will execute first, this method,
+
+291
+00:11:43,000 --> 00:11:46,000
+but this particular method B constructor is
+
+292
+00:11:46,000 --> 00:11:49,000
+executing this, which is the default constructor.
+
+293
+00:11:49,000 --> 00:11:52,000
+The default constructor executes the super which goes here,
+
+294
+00:11:52,000 --> 00:11:57,000
+it'll execute in A, it'll execute in B and then in B int.
+
+295
+00:11:57,000 --> 00:12:00,000
+So that's what is, which is this keyword
+
+296
+00:12:00,000 --> 00:12:02,000
+and also this method and super method.
+
+297
+00:12:02,000 --> 00:12:05,000
+So this method execute the construct of a same class,
+
+298
+00:12:05,000 --> 00:12:08,000
+super method executes the construct of a super class.
+
+299
+00:12:08,000 --> 00:12:09,000
+So yeah, that's it from this video.
+
+300
+00:12:09,000 --> 00:12:10,000
+I hope you enjoyed it.
+
+301
+00:12:10,000 --> 00:12:13,000
+Let's see what we can do in the next video.
+
diff --git a/02 - Core Java/056 Method Overriding_en.srt b/02 - Core Java/056 Method Overriding_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..f57c7185cacbe7f98db8e8e91ade1cb659aa451d
--- /dev/null
+++ b/02 - Core Java/056 Method Overriding_en.srt	
@@ -0,0 +1,808 @@
+1
+00:00:00,000 --> 00:00:02,000
+(bright music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: So once we talked about inheritance
+
+3
+00:00:05,000 --> 00:00:07,000
+and method overloading as well, right?
+
+4
+00:00:07,000 --> 00:00:08,000
+We have talked about method overloading.
+
+5
+00:00:08,000 --> 00:00:09,000
+In this video,
+
+6
+00:00:09,000 --> 00:00:12,000
+let's talk about method overriding. That's right.
+
+7
+00:00:12,000 --> 00:00:14,000
+So we have two different method,
+
+8
+00:00:14,000 --> 00:00:16,000
+overloading and method overriding.
+
+9
+00:00:16,000 --> 00:00:17,000
+So let's talk about overriding here.
+
+10
+00:00:17,000 --> 00:00:18,000
+So for that, what I will do is
+
+11
+00:00:18,000 --> 00:00:20,000
+I will just try to keep it simple again
+
+12
+00:00:20,000 --> 00:00:22,000
+and let's use the class A
+
+13
+00:00:22,000 --> 00:00:25,000
+and inside this class A, let's say we have a method.
+
+14
+00:00:25,000 --> 00:00:27,000
+So I will just remove this part.
+
+15
+00:00:27,000 --> 00:00:31,000
+And here I would say public void show.
+
+16
+00:00:31,000 --> 00:00:32,000
+Just to keep it simple,
+
+17
+00:00:32,000 --> 00:00:33,000
+I'm using a very simple example here,
+
+18
+00:00:33,000 --> 00:00:36,000
+which is show which prints something.
+
+19
+00:00:36,000 --> 00:00:39,000
+Let's say it prints in show, okay.
+
+20
+00:00:39,000 --> 00:00:42,000
+Now if you have a method inside a class,
+
+21
+00:00:42,000 --> 00:00:43,000
+of course you can create the object
+
+22
+00:00:43,000 --> 00:00:45,000
+and you can call the method, right,
+
+23
+00:00:45,000 --> 00:00:46,000
+and we have seen that.
+
+24
+00:00:46,000 --> 00:00:48,000
+So let's say if I go back to my main method,
+
+25
+00:00:48,000 --> 00:00:51,000
+if I say A obj = new A,
+
+26
+00:00:51,000 --> 00:00:56,000
+and I can simply say obj.show and it'll work, right.
+
+27
+00:00:56,000 --> 00:00:57,000
+And it should work.
+
+28
+00:00:57,000 --> 00:00:59,000
+That's what we have done from a long time.
+
+29
+00:00:59,000 --> 00:01:02,000
+So let's compile this code and run.
+
+30
+00:01:02,000 --> 00:01:04,000
+And you can see it prints in show.
+
+31
+00:01:04,000 --> 00:01:06,000
+Just to keep it simple, we have went
+
+32
+00:01:06,000 --> 00:01:08,000
+with a very simple example.
+
+33
+00:01:08,000 --> 00:01:09,000
+Now what I wanna do is
+
+34
+00:01:09,000 --> 00:01:12,000
+I want to get a class which is class B,
+
+35
+00:01:12,000 --> 00:01:15,000
+and I want this class B to extends class A.
+
+36
+00:01:15,000 --> 00:01:18,000
+And of course when you talk about inheritance,
+
+37
+00:01:18,000 --> 00:01:19,000
+this method of show,
+
+38
+00:01:19,000 --> 00:01:21,000
+it also will be available inside Class B, right.
+
+39
+00:01:21,000 --> 00:01:25,000
+So if I create object of class B instead of A,
+
+40
+00:01:25,000 --> 00:01:28,000
+it'll also work because that's how inheritance works, right.
+
+41
+00:01:28,000 --> 00:01:31,000
+So if I go back, compile and run, it works.
+
+42
+00:01:31,000 --> 00:01:33,000
+You can see we got in show.
+
+43
+00:01:33,000 --> 00:01:37,000
+What I do now is I will also print in A show
+
+44
+00:01:37,000 --> 00:01:40,000
+just to differentiate that this is getting printed
+
+45
+00:01:40,000 --> 00:01:41,000
+in the A class, okay.
+
+46
+00:01:41,000 --> 00:01:43,000
+Now the thing is,
+
+47
+00:01:43,000 --> 00:01:47,000
+what if you want to have a different definition of it?
+
+48
+00:01:47,000 --> 00:01:48,000
+Okay, why do we need different definition?
+
+49
+00:01:48,000 --> 00:01:52,000
+Let's say we got two methods here, public void config.
+
+50
+00:01:52,000 --> 00:01:54,000
+So let's say we have this method which is called config.
+
+51
+00:01:54,000 --> 00:01:55,000
+I don't know what it'll do.
+
+52
+00:01:55,000 --> 00:01:58,000
+Just to keep it simple, I will just say S out
+
+53
+00:01:58,000 --> 00:02:01,000
+and I will say this is in a config, okay.
+
+54
+00:02:01,000 --> 00:02:03,000
+And let's say they have different implementation,
+
+55
+00:02:03,000 --> 00:02:04,000
+they have different statements.
+
+56
+00:02:04,000 --> 00:02:06,000
+At this point, we are not focusing on statements.
+
+57
+00:02:06,000 --> 00:02:08,000
+We are here to understand the concept, right?
+
+58
+00:02:08,000 --> 00:02:10,000
+So let's say it does something,
+
+59
+00:02:10,000 --> 00:02:12,000
+so method and config does something
+
+60
+00:02:12,000 --> 00:02:15,000
+and I can actually call both the methods, not just one.
+
+61
+00:02:15,000 --> 00:02:17,000
+I can call config as well, okay?
+
+62
+00:02:17,000 --> 00:02:21,000
+And if I compile and run this code, it works.
+
+63
+00:02:21,000 --> 00:02:24,000
+You can see it says in A show in A config.
+
+64
+00:02:24,000 --> 00:02:28,000
+Now, let's say I want a different definition for show, okay,
+
+65
+00:02:28,000 --> 00:02:29,000
+not for config.
+
+66
+00:02:29,000 --> 00:02:32,000
+So basically what I want is when it comes to B,
+
+67
+00:02:32,000 --> 00:02:36,000
+and when I call show, it should print in B show.
+
+68
+00:02:36,000 --> 00:02:39,000
+How do I do that? How do I change the execution?
+
+69
+00:02:39,000 --> 00:02:41,000
+So what I want is when I call show,
+
+70
+00:02:41,000 --> 00:02:43,000
+it should not call the show of A
+
+71
+00:02:43,000 --> 00:02:46,000
+because show of A will print in A show.
+
+72
+00:02:46,000 --> 00:02:47,000
+I want to use config as it is.
+
+73
+00:02:47,000 --> 00:02:49,000
+So I can't even remove this inheritance.
+
+74
+00:02:49,000 --> 00:02:52,000
+If I remove this, and if I define the methods,
+
+75
+00:02:52,000 --> 00:02:53,000
+of course I can define show,
+
+76
+00:02:53,000 --> 00:02:57,000
+but then I want this config to be coming from A.
+
+77
+00:02:57,000 --> 00:02:58,000
+So of course you have to keep it.
+
+78
+00:02:58,000 --> 00:03:02,000
+You have to say Class B extends A, because we want config.
+
+79
+00:03:02,000 --> 00:03:05,000
+What we don't want of A is show
+
+80
+00:03:05,000 --> 00:03:07,000
+because it is printing in A show.
+
+81
+00:03:07,000 --> 00:03:08,000
+I wanna do something else.
+
+82
+00:03:08,000 --> 00:03:11,000
+In that scenario, you can say public void show,
+
+83
+00:03:11,000 --> 00:03:13,000
+you can write the same method name
+
+84
+00:03:13,000 --> 00:03:14,000
+or maybe a different name.
+
+85
+00:03:14,000 --> 00:03:17,000
+You can say in show1, I mean show1
+
+86
+00:03:17,000 --> 00:03:21,000
+and you can print here in B show.
+
+87
+00:03:21,000 --> 00:03:22,000
+I mean of course you can do this.
+
+88
+00:03:22,000 --> 00:03:24,000
+The only thing is
+
+89
+00:03:24,000 --> 00:03:26,000
+if you execute this code now,
+
+90
+00:03:26,000 --> 00:03:28,000
+it'll still print in A show.
+
+91
+00:03:28,000 --> 00:03:30,000
+You know why? is because we are calling show,
+
+92
+00:03:30,000 --> 00:03:32,000
+and both these methods are different.
+
+93
+00:03:32,000 --> 00:03:36,000
+One with name show and one with name show1, okay.
+
+94
+00:03:36,000 --> 00:03:37,000
+That means if I call show1, then it'll work,
+
+95
+00:03:37,000 --> 00:03:40,000
+then it'll print in B show.
+
+96
+00:03:40,000 --> 00:03:41,000
+But what I want is
+
+97
+00:03:41,000 --> 00:03:43,000
+I want them to have a same name.
+
+98
+00:03:43,000 --> 00:03:46,000
+I want my this method, which is show
+
+99
+00:03:46,000 --> 00:03:49,000
+should override the method here.
+
+100
+00:03:49,000 --> 00:03:50,000
+Is it possible?
+
+101
+00:03:50,000 --> 00:03:51,000
+And the answer is yes.
+
+102
+00:03:51,000 --> 00:03:53,000
+In Java we get this amazing feature where
+
+103
+00:03:53,000 --> 00:03:56,000
+you can basically override the methods
+
+104
+00:03:56,000 --> 00:03:57,000
+of the patent class.
+
+105
+00:03:57,000 --> 00:04:02,000
+So of course you want everything except this part. Okay.
+
+106
+00:04:02,000 --> 00:04:03,000
+I mean, except this show method.
+
+107
+00:04:03,000 --> 00:04:05,000
+I want config, but I don't want show.
+
+108
+00:04:05,000 --> 00:04:06,000
+Now, let me give you one more example here.
+
+109
+00:04:06,000 --> 00:04:08,000
+Remember when we talked about inheritance,
+
+110
+00:04:08,000 --> 00:04:09,000
+I have used an example
+
+111
+00:04:09,000 --> 00:04:12,000
+where I was not having any phone in my 10 standard
+
+112
+00:04:12,000 --> 00:04:15,000
+and my father had a phone, which is 3310.
+
+113
+00:04:15,000 --> 00:04:18,000
+Now if you ask me at that point, which phone I have,
+
+114
+00:04:18,000 --> 00:04:22,000
+I would just say 3310 because that's my father's phone.
+
+115
+00:04:22,000 --> 00:04:24,000
+But after two years, when I was in my 12 standard,
+
+116
+00:04:24,000 --> 00:04:25,000
+I got my own phone.
+
+117
+00:04:25,000 --> 00:04:27,000
+I got Motorola C168.
+
+118
+00:04:27,000 --> 00:04:29,000
+Again, not a smart phone,
+
+119
+00:04:29,000 --> 00:04:32,000
+but it was good, it was a very slim phone.
+
+120
+00:04:32,000 --> 00:04:35,000
+So when now if you ask me which phone I have,
+
+121
+00:04:35,000 --> 00:04:37,000
+I will say I have Motorola C168.
+
+122
+00:04:37,000 --> 00:04:40,000
+My father still had 3310.
+
+123
+00:04:40,000 --> 00:04:41,000
+So here, if you can see,
+
+124
+00:04:41,000 --> 00:04:43,000
+if someone ask my father,
+
+125
+00:04:43,000 --> 00:04:45,000
+father will say, I have 3310.
+
+126
+00:04:45,000 --> 00:04:48,000
+If you ask me, I have a choice of saying 3310,
+
+127
+00:04:48,000 --> 00:04:52,000
+but I will go for C168, which is my phone, right?
+
+128
+00:04:52,000 --> 00:04:55,000
+So you always give preference to your own features first.
+
+129
+00:04:55,000 --> 00:04:58,000
+Example, if you call show here,
+
+130
+00:04:58,000 --> 00:04:59,000
+it'll execute the method of B
+
+131
+00:04:59,000 --> 00:05:01,000
+instead of executing the method of A.
+
+132
+00:05:01,000 --> 00:05:04,000
+So basically this method show
+
+133
+00:05:04,000 --> 00:05:07,000
+overrides the method of A here.
+
+134
+00:05:07,000 --> 00:05:10,000
+And we can simply execute, compile, and run.
+
+135
+00:05:10,000 --> 00:05:12,000
+You can see it prints in B show.
+
+136
+00:05:12,000 --> 00:05:13,000
+Now this will make much more sense
+
+137
+00:05:13,000 --> 00:05:16,000
+when we say we are creating not A,
+
+138
+00:05:16,000 --> 00:05:18,000
+but we are creating a calculator
+
+139
+00:05:18,000 --> 00:05:20,000
+which has a method called let's say,
+
+140
+00:05:20,000 --> 00:05:22,000
+let me remove config for some time.
+
+141
+00:05:22,000 --> 00:05:25,000
+Let's say that we have a method called add,
+
+142
+00:05:25,000 --> 00:05:28,000
+and this will return a value, okay.
+
+143
+00:05:28,000 --> 00:05:30,000
+And here, instead of printing this,
+
+144
+00:05:30,000 --> 00:05:31,000
+I can simply accept two values.
+
+145
+00:05:31,000 --> 00:05:35,000
+I can say int n1, int n2,
+
+146
+00:05:35,000 --> 00:05:37,000
+and here we have done this before
+
+147
+00:05:37,000 --> 00:05:38,000
+and that's why I'm writing this code very fast.
+
+148
+00:05:38,000 --> 00:05:43,000
+I can say return and n1+n2. Okay.
+
+149
+00:05:43,000 --> 00:05:46,000
+So if your class, which is instead of saying B,
+
+150
+00:05:46,000 --> 00:05:50,000
+I can say Advanced Calc, which is extending calc.
+
+151
+00:05:50,000 --> 00:05:52,000
+It'll also have some features.
+
+152
+00:05:52,000 --> 00:05:56,000
+But let's say I want to add two numbers,
+
+153
+00:05:56,000 --> 00:05:57,000
+which will also take int
+
+154
+00:05:57,000 --> 00:05:59,000
+and it'll have the same parameter, okay,
+
+155
+00:05:59,000 --> 00:06:01,000
+because in method overloading we have seen
+
+156
+00:06:01,000 --> 00:06:03,000
+it can have the same method name
+
+157
+00:06:03,000 --> 00:06:04,000
+but different parameters.
+
+158
+00:06:04,000 --> 00:06:06,000
+Here in method overriding,
+
+159
+00:06:06,000 --> 00:06:08,000
+it'll be same name, same parameters as well.
+
+160
+00:06:08,000 --> 00:06:10,000
+I mean same type of parameters,
+
+161
+00:06:10,000 --> 00:06:12,000
+not the name, doesn't matter name,
+
+162
+00:06:12,000 --> 00:06:13,000
+let's say n1, n2
+
+163
+00:06:13,000 --> 00:06:16,000
+and it'll have the same name, same number of parameters,
+
+164
+00:06:16,000 --> 00:06:18,000
+same type of parameters,
+
+165
+00:06:18,000 --> 00:06:19,000
+but it'll have a different behavior.
+
+166
+00:06:19,000 --> 00:06:20,000
+Let's say n1+n2+1.
+
+167
+00:06:20,000 --> 00:06:22,000
+I'm just adding extra one there.
+
+168
+00:06:22,000 --> 00:06:27,000
+So what I want is if I comment this section, okay,
+
+169
+00:06:27,000 --> 00:06:28,000
+at this point I'm not overriding it,
+
+170
+00:06:28,000 --> 00:06:31,000
+I just have add method inside calc,
+
+171
+00:06:31,000 --> 00:06:34,000
+and if I create the object of advanced calculator
+
+172
+00:06:34,000 --> 00:06:38,000
+by saying Advanced Calculator obj = new Advanced Calculator,
+
+173
+00:06:38,000 --> 00:06:42,000
+and if I try to call the add method by passing 3 and 4,
+
+174
+00:06:42,000 --> 00:06:44,000
+of course 3 and 4 is 7.
+
+175
+00:06:44,000 --> 00:06:46,000
+So if I get this value somewhere,
+
+176
+00:06:46,000 --> 00:06:48,000
+if I say int r1 =,
+
+177
+00:06:48,000 --> 00:06:51,000
+and if I print the value for r1,
+
+178
+00:06:51,000 --> 00:06:53,000
+and again, since we have done this code before,
+
+179
+00:06:53,000 --> 00:06:55,000
+I'm just typing it fast.
+
+180
+00:06:55,000 --> 00:06:57,000
+Now, what do you think? What will the output?
+
+181
+00:06:57,000 --> 00:06:58,000
+I'm passing 3 and 4.
+
+182
+00:06:58,000 --> 00:07:01,000
+So of course it'll first search for this method add
+
+183
+00:07:01,000 --> 00:07:03,000
+inside the same class.
+
+184
+00:07:03,000 --> 00:07:05,000
+Of course, we don't have that method.
+
+185
+00:07:05,000 --> 00:07:07,000
+So it'll go to the upper class by saying,
+
+186
+00:07:07,000 --> 00:07:10,000
+Hey, you know calc, you are my parent class,
+
+187
+00:07:10,000 --> 00:07:14,000
+I'm searching for add with you and yes, it is available.
+
+188
+00:07:14,000 --> 00:07:17,000
+So basically we can just compile this code and run.
+
+189
+00:07:17,000 --> 00:07:20,000
+You can see we got 7 and that actually works.
+
+190
+00:07:20,000 --> 00:07:23,000
+But now I want a different definition for add,
+
+191
+00:07:23,000 --> 00:07:24,000
+I just want some changes.
+
+192
+00:07:24,000 --> 00:07:26,000
+Instead of adding those two numbers,
+
+193
+00:07:26,000 --> 00:07:29,000
+it should also add 1 at the end, okay.
+
+194
+00:07:29,000 --> 00:07:33,000
+So if I compile this code now and run, it'll print 8.
+
+195
+00:07:33,000 --> 00:07:37,000
+So this add is overriding the add method of calculator.
+
+196
+00:07:37,000 --> 00:07:40,000
+Okay, just remove this statement, that's extra.
+
+197
+00:07:40,000 --> 00:07:44,000
+So this concept is called method overriding.
+
+198
+00:07:44,000 --> 00:07:47,000
+So this method is overriding the method here.
+
+199
+00:07:48,000 --> 00:07:50,000
+I hope that makes sense.
+
+200
+00:07:50,000 --> 00:07:52,000
+So this is method overriding.
+
+201
+00:07:52,000 --> 00:07:54,000
+In fact, there is one more trick here,
+
+202
+00:07:54,000 --> 00:07:56,000
+which we'll discuss in the next video.
+
diff --git a/02 - Core Java/056 Source-code.url b/02 - Core Java/056 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/056 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/057 Packages_en.srt b/02 - Core Java/057 Packages_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..dc6caddf47e887e266155abe5fd3eda5dae151fc
--- /dev/null
+++ b/02 - Core Java/057 Packages_en.srt	
@@ -0,0 +1,1252 @@
+1
+00:00:00,000 --> 00:00:03,000
+(soft instrumental music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: In this video let's talk about packages.
+
+3
+00:00:05,000 --> 00:00:07,000
+The thing is, whenever you have a file,
+
+4
+00:00:07,000 --> 00:00:11,000
+it doesn't matter is it music files or documents or code,
+
+5
+00:00:11,000 --> 00:00:13,000
+we normally put them in a folder, right?
+
+6
+00:00:13,000 --> 00:00:16,000
+And then we create a folder structure as well.
+
+7
+00:00:16,000 --> 00:00:19,000
+In fact, I remember in my college days when we used
+
+8
+00:00:19,000 --> 00:00:20,000
+to store different songs
+
+9
+00:00:20,000 --> 00:00:22,000
+we used to create different folders.
+
+10
+00:00:22,000 --> 00:00:26,000
+Like we have a Songs folder, then inside that we have
+
+11
+00:00:26,000 --> 00:00:30,000
+Rock Songs, DJ Songs, Sad Songs, Romantic Songs.
+
+12
+00:00:30,000 --> 00:00:33,000
+And in fact in that as well, when you go to Sad Songs
+
+13
+00:00:33,000 --> 00:00:36,000
+we can have Normal Sad Songs, Ultimate Sad Songs.
+
+14
+00:00:36,000 --> 00:00:38,000
+Okay, now that's exaggeration, but we do that, right?
+
+15
+00:00:38,000 --> 00:00:39,000
+We create a structure there.
+
+16
+00:00:39,000 --> 00:00:42,000
+In the same way, when you talk about Java project
+
+17
+00:00:42,000 --> 00:00:44,000
+you will not be creating one or two files, right?
+
+18
+00:00:44,000 --> 00:00:46,000
+It will be having multiple files.
+
+19
+00:00:46,000 --> 00:00:48,000
+Sometimes your project can have
+
+20
+00:00:48,000 --> 00:00:51,000
+let's say 200 files, 300 files.
+
+21
+00:00:51,000 --> 00:00:52,000
+Okay, maybe most of the time
+
+22
+00:00:52,000 --> 00:00:54,000
+when you have a complex project.
+
+23
+00:00:54,000 --> 00:00:57,000
+Now, how will you put all these files in one folder?
+
+24
+00:00:57,000 --> 00:00:59,000
+You can actually, you can put everything in one folder.
+
+25
+00:00:59,000 --> 00:01:02,000
+Now, if you see our project structure here,
+
+26
+00:01:02,000 --> 00:01:04,000
+what we did is we have this folder called CODES.
+
+27
+00:01:04,000 --> 00:01:07,000
+And in this CODES we have all of the files.
+
+28
+00:01:07,000 --> 00:01:09,000
+In fact, we only have three files now,
+
+29
+00:01:09,000 --> 00:01:11,000
+but just imagine we have more files.
+
+30
+00:01:11,000 --> 00:01:13,000
+Imagine if we have 100 files.
+
+31
+00:01:13,000 --> 00:01:15,000
+It's okay to put them in one folder,
+
+32
+00:01:15,000 --> 00:01:18,000
+but it's always better if you can create a structure
+
+33
+00:01:18,000 --> 00:01:21,000
+where you can have few files in one folder
+
+34
+00:01:21,000 --> 00:01:23,000
+and few files in another folder.
+
+35
+00:01:23,000 --> 00:01:26,000
+And then you can have a folder inside a folder.
+
+36
+00:01:26,000 --> 00:01:27,000
+Now, normally this type of pattern
+
+37
+00:01:27,000 --> 00:01:29,000
+in Java is called packages.
+
+38
+00:01:29,000 --> 00:01:32,000
+Normally you store files in a package.
+
+39
+00:01:32,000 --> 00:01:35,000
+So, yeah, that's right, the folder is package here.
+
+40
+00:01:35,000 --> 00:01:38,000
+And of course one package can be a part of another package
+
+41
+00:01:38,000 --> 00:01:40,000
+the way you have folders inside a folder.
+
+42
+00:01:40,000 --> 00:01:42,000
+So, how do we do that here in Java?
+
+43
+00:01:42,000 --> 00:01:44,000
+So, just to make you understand,
+
+44
+00:01:44,000 --> 00:01:45,000
+let's say we have these two files,
+
+45
+00:01:45,000 --> 00:01:47,000
+AdvancedCalculator and Calculator.
+
+46
+00:01:47,000 --> 00:01:49,000
+Now, these two files are related, right?
+
+47
+00:01:49,000 --> 00:01:51,000
+They both work for the calculator,
+
+48
+00:01:51,000 --> 00:01:55,000
+so it is a good idea to put them in one folder.
+
+49
+00:01:55,000 --> 00:01:56,000
+Now, how will you do that?
+
+50
+00:01:56,000 --> 00:01:58,000
+You have an option here of creating a new folder.
+
+51
+00:01:58,000 --> 00:01:59,000
+That's one way.
+
+52
+00:01:59,000 --> 00:02:01,000
+Or you can, what you can do is you can just come back
+
+53
+00:02:01,000 --> 00:02:04,000
+on top of your class and say you can create a package.
+
+54
+00:02:04,000 --> 00:02:06,000
+So, the keyword which you use
+
+55
+00:02:06,000 --> 00:02:07,000
+to create a package is called package,
+
+56
+00:02:07,000 --> 00:02:10,000
+and you can put this class in that particular package.
+
+57
+00:02:10,000 --> 00:02:13,000
+Let's say the package name is tools, right?
+
+58
+00:02:13,000 --> 00:02:15,000
+So, of course you can create any package name,
+
+59
+00:02:15,000 --> 00:02:17,000
+but it should have an, it should make some sense.
+
+60
+00:02:17,000 --> 00:02:21,000
+So, you can see I'm saying that they are tools, okay?
+
+61
+00:02:21,000 --> 00:02:24,000
+And the thing is you can see we are getting an error.
+
+62
+00:02:24,000 --> 00:02:26,000
+It says that declared package tools
+
+63
+00:02:26,000 --> 00:02:29,000
+does not match the expected package.
+
+64
+00:02:29,000 --> 00:02:33,000
+The thing is you don't have Calc inside the package.
+
+65
+00:02:33,000 --> 00:02:35,000
+In fact, most of the IDs will give you an option
+
+66
+00:02:35,000 --> 00:02:39,000
+of directly, if I click on Quick Fix, yeah.
+
+67
+00:02:39,000 --> 00:02:40,000
+So, you can see most of the IDs,
+
+68
+00:02:40,000 --> 00:02:42,000
+doesn't matter which ID you're using,
+
+69
+00:02:42,000 --> 00:02:44,000
+in VS Code we have this option.
+
+70
+00:02:44,000 --> 00:02:46,000
+In most of the famous ID you will get this option
+
+71
+00:02:46,000 --> 00:02:50,000
+of doing something, some red symbol or something like that.
+
+72
+00:02:50,000 --> 00:02:52,000
+Here we have an option of Quick Fix.
+
+73
+00:02:52,000 --> 00:02:57,000
+If I click on that it says Move Calc.java to package tools.
+
+74
+00:02:57,000 --> 00:02:59,000
+Okay, that is a good idea.
+
+75
+00:02:59,000 --> 00:03:00,000
+We can click on this,
+
+76
+00:03:00,000 --> 00:03:04,000
+and you can see it created a folder called tools.
+
+77
+00:03:04,000 --> 00:03:07,000
+And now we can actually move this to tools as well.
+
+78
+00:03:07,000 --> 00:03:09,000
+The only thing is when you do that
+
+79
+00:03:09,000 --> 00:03:13,000
+and when you go to this particular class, okay,
+
+80
+00:03:13,000 --> 00:03:14,000
+it has already done the changes.
+
+81
+00:03:14,000 --> 00:03:16,000
+You can see I have not written this.
+
+82
+00:03:16,000 --> 00:03:19,000
+It is already there thanks to VS Code and the IDE,
+
+83
+00:03:20,000 --> 00:03:21,000
+so basically you get this here.
+
+84
+00:03:21,000 --> 00:03:23,000
+So, it's always a good idea
+
+85
+00:03:23,000 --> 00:03:25,000
+to put your classes in a package.
+
+86
+00:03:25,000 --> 00:03:28,000
+You can create a complex structure.
+
+87
+00:03:28,000 --> 00:03:31,000
+If you want you can create one more folder here.
+
+88
+00:03:31,000 --> 00:03:35,000
+Let's say we got a folder called database,
+
+89
+00:03:35,000 --> 00:03:37,000
+or maybe dbconnections or dbclasses,
+
+90
+00:03:37,000 --> 00:03:39,000
+or maybe you can just simply say db.
+
+91
+00:03:39,000 --> 00:03:41,000
+Now, this db will have all the database connections.
+
+92
+00:03:41,000 --> 00:03:44,000
+So, let's say if you want to create some files
+
+93
+00:03:44,000 --> 00:03:47,000
+which will connect with MySQL, Oracle or,
+
+94
+00:03:47,000 --> 00:03:48,000
+it does something with database,
+
+95
+00:03:48,000 --> 00:03:52,000
+so you can put all those classes in database folder, okay?
+
+96
+00:03:52,000 --> 00:03:55,000
+Now, that's how you create a project structure here, okay?
+
+97
+00:03:55,000 --> 00:03:57,000
+The only thing is if you want,
+
+98
+00:03:57,000 --> 00:03:58,000
+if you have this structure here.
+
+99
+00:03:58,000 --> 00:04:01,000
+Let's say if you have Calc and Demo, AdvancedCalc,
+
+100
+00:04:01,000 --> 00:04:03,000
+and if you can see both are in a package now.
+
+101
+00:04:03,000 --> 00:04:07,000
+The only problem we will face is if you go to Demo,
+
+102
+00:04:07,000 --> 00:04:10,000
+and you can see Demo is not a part of any package.
+
+103
+00:04:10,000 --> 00:04:13,000
+Normally you put the main class,
+
+104
+00:04:13,000 --> 00:04:16,000
+so the class which has a main method separately,
+
+105
+00:04:16,000 --> 00:04:17,000
+outside the package so that you can
+
+106
+00:04:17,000 --> 00:04:19,000
+easily access other classes.
+
+107
+00:04:19,000 --> 00:04:21,000
+Okay, when I say easily access other classes can I do that?
+
+108
+00:04:21,000 --> 00:04:24,000
+Can I create object of Calc here?
+
+109
+00:04:24,000 --> 00:04:26,000
+So, if I say Calc obj equal to new Calc,
+
+110
+00:04:26,000 --> 00:04:28,000
+which was working earlier,
+
+111
+00:04:28,000 --> 00:04:31,000
+if you remember our previous examples.
+
+112
+00:04:31,000 --> 00:04:32,000
+It's not working now.
+
+113
+00:04:32,000 --> 00:04:34,000
+You can see it says Calc cannot be resolved.
+
+114
+00:04:34,000 --> 00:04:35,000
+What's wrong?
+
+115
+00:04:35,000 --> 00:04:38,000
+The problem is Demo and Calc,
+
+116
+00:04:38,000 --> 00:04:40,000
+now they are in two different folders.
+
+117
+00:04:40,000 --> 00:04:42,000
+You can't directly access it.
+
+118
+00:04:42,000 --> 00:04:44,000
+Okay, so when I say you cannot directly access it
+
+119
+00:04:44,000 --> 00:04:46,000
+do we have an indirect way?
+
+120
+00:04:46,000 --> 00:04:48,000
+Yes, we have an indirect way.
+
+121
+00:04:48,000 --> 00:04:51,000
+So, what you can do is if you see this bubble
+
+122
+00:04:51,000 --> 00:04:53,000
+it says Import Calc, that's right.
+
+123
+00:04:53,000 --> 00:04:56,000
+If you want to use Calc in your particular class
+
+124
+00:04:56,000 --> 00:04:58,000
+you have to say import Calc.
+
+125
+00:04:58,000 --> 00:05:00,000
+But then Calc belong where?
+
+126
+00:05:00,000 --> 00:05:03,000
+Calc belongs to tools.Calc.
+
+127
+00:05:03,000 --> 00:05:05,000
+So, basically you have to mention the package name
+
+128
+00:05:05,000 --> 00:05:07,000
+and then you have to mention the class name,
+
+129
+00:05:07,000 --> 00:05:08,000
+whichever you want to import.
+
+130
+00:05:08,000 --> 00:05:10,000
+And now you can see there's no issue.
+
+131
+00:05:10,000 --> 00:05:12,000
+How about AdvancedCalculator?
+
+132
+00:05:12,000 --> 00:05:14,000
+If I want to use AdvancedCalculator,
+
+133
+00:05:14,000 --> 00:05:17,000
+obj1 is equal to new AdvancedCalculator.
+
+134
+00:05:17,000 --> 00:05:20,000
+Okay, now you cannot access this one, you know why?
+
+135
+00:05:20,000 --> 00:05:23,000
+It's because we have only imported Calc,
+
+136
+00:05:23,000 --> 00:05:25,000
+not AdvancedCalculator.
+
+137
+00:05:25,000 --> 00:05:26,000
+How will you import this?
+
+138
+00:05:26,000 --> 00:05:27,000
+You're right.
+
+139
+00:05:27,000 --> 00:05:30,000
+Just come back here and say import tools.AdvancedCalculator.
+
+140
+00:05:31,000 --> 00:05:33,000
+So, whichever class you want to use
+
+141
+00:05:33,000 --> 00:05:35,000
+you can just import them.
+
+142
+00:05:35,000 --> 00:05:38,000
+In fact, Java internally has a lot of classes.
+
+143
+00:05:38,000 --> 00:05:39,000
+Example, let's say one of the classes,
+
+144
+00:05:39,000 --> 00:05:42,000
+which we're going to see in future, which is let's say list.
+
+145
+00:05:42,000 --> 00:05:46,000
+Now, when we use list, which is inbuilt class,
+
+146
+00:05:46,000 --> 00:05:47,000
+or inbuilt interface, what is interface?
+
+147
+00:05:47,000 --> 00:05:48,000
+We'll talk about that later.
+
+148
+00:05:48,000 --> 00:05:50,000
+Or maybe at this point we can talk about
+
+149
+00:05:50,000 --> 00:05:53,000
+let's say ArrayList, which is a class.
+
+150
+00:05:53,000 --> 00:05:56,000
+When we use ArrayList and when you create object of it,
+
+151
+00:05:56,000 --> 00:05:59,000
+I will say list is equal to new ArrayList.
+
+152
+00:06:00,000 --> 00:06:01,000
+Now, the moment you do that
+
+153
+00:06:01,000 --> 00:06:03,000
+it will also come from a package.
+
+154
+00:06:03,000 --> 00:06:06,000
+You can see it is now given by the IDE,
+
+155
+00:06:06,000 --> 00:06:08,000
+it is auto-completing it.
+
+156
+00:06:08,000 --> 00:06:10,000
+But if I remove this line you can see
+
+157
+00:06:10,000 --> 00:06:10,000
+it will give you error.
+
+158
+00:06:10,000 --> 00:06:12,000
+It says ArrayList cannot be found.
+
+159
+00:06:12,000 --> 00:06:14,000
+So, we have to import this one as well,
+
+160
+00:06:14,000 --> 00:06:16,000
+and this belongs to a package.
+
+161
+00:06:16,000 --> 00:06:21,000
+Now, that package is import java.util.ArrayList.
+
+162
+00:06:22,000 --> 00:06:23,000
+This you have to import.
+
+163
+00:06:23,000 --> 00:06:26,000
+Now, you might be thinking why we have two dots here,
+
+164
+00:06:26,000 --> 00:06:28,000
+java.util, how it looks like.
+
+165
+00:06:28,000 --> 00:06:30,000
+So, basically we have a Java folder.
+
+166
+00:06:30,000 --> 00:06:33,000
+Inside Java folder we have a util folder.
+
+167
+00:06:33,000 --> 00:06:36,000
+So, it's the folder inside the folder,
+
+168
+00:06:36,000 --> 00:06:38,000
+and Java has multiple folders if you can see.
+
+169
+00:06:38,000 --> 00:06:41,000
+Java., we have applet folder,
+
+170
+00:06:41,000 --> 00:06:46,000
+we have awt folder, beans folder, lang folder, io folder,
+
+171
+00:06:46,000 --> 00:06:47,000
+and all those things.
+
+172
+00:06:47,000 --> 00:06:51,000
+So, in general whatever class you use in Java
+
+173
+00:06:51,000 --> 00:06:53,000
+belongs to a package.
+
+174
+00:06:53,000 --> 00:06:55,000
+Let me repeat, whichever class,
+
+175
+00:06:55,000 --> 00:06:59,000
+inbuilt class which you use in Java, belongs to a package.
+
+176
+00:06:59,000 --> 00:07:02,000
+Now you'll be saying okay, everything makes sense,
+
+177
+00:07:02,000 --> 00:07:05,000
+but don't you think String is also a class?
+
+178
+00:07:05,000 --> 00:07:09,000
+And one of our favorite class, which is System.
+
+179
+00:07:09,000 --> 00:07:11,000
+System is also a class, right?
+
+180
+00:07:11,000 --> 00:07:14,000
+So, when we are using System we have never imported it.
+
+181
+00:07:14,000 --> 00:07:16,000
+So, when I say System.out.println,
+
+182
+00:07:17,000 --> 00:07:19,000
+there was no need to import the package.
+
+183
+00:07:19,000 --> 00:07:21,000
+But does System belong to a package?
+
+184
+00:07:21,000 --> 00:07:22,000
+And the answer is yes.
+
+185
+00:07:22,000 --> 00:07:27,000
+If I go to System and if I go on top here, can you see that?
+
+186
+00:07:27,000 --> 00:07:28,000
+It says package.
+
+187
+00:07:28,000 --> 00:07:30,000
+So, this class, System class,
+
+188
+00:07:30,000 --> 00:07:32,000
+belongs to our package java.lang,
+
+189
+00:07:32,000 --> 00:07:33,000
+but we never imported it.
+
+190
+00:07:33,000 --> 00:07:37,000
+The thing is, by default every Java file will have
+
+191
+00:07:37,000 --> 00:07:40,000
+java.lang by default imported.
+
+192
+00:07:40,000 --> 00:07:42,000
+So, even if you don't mention that it's there.
+
+193
+00:07:42,000 --> 00:07:45,000
+This line is there even if you don't mention.
+
+194
+00:07:45,000 --> 00:07:48,000
+Now, the thing is it's actually this, not this line.
+
+195
+00:07:48,000 --> 00:07:52,000
+What is by default is this, java.lang.*.
+
+196
+00:07:52,000 --> 00:07:53,000
+Now, what is this star?
+
+197
+00:07:53,000 --> 00:07:56,000
+Now, in one particular folder if you have multiple files,
+
+198
+00:07:56,000 --> 00:08:00,000
+and if you want all the files you can simply say star
+
+199
+00:08:00,000 --> 00:08:01,000
+just like we have tools here.
+
+200
+00:08:01,000 --> 00:08:03,000
+In tools we only have two files,
+
+201
+00:08:03,000 --> 00:08:05,000
+and we are importing both.
+
+202
+00:08:05,000 --> 00:08:06,000
+So, can we just do that?
+
+203
+00:08:06,000 --> 00:08:07,000
+Yes, we can.
+
+204
+00:08:07,000 --> 00:08:10,000
+So, we can simply put a star here, our job is done.
+
+205
+00:08:10,000 --> 00:08:13,000
+And by doing that I also removed the list.
+
+206
+00:08:13,000 --> 00:08:15,000
+We don't even need that, you know that.
+
+207
+00:08:15,000 --> 00:08:17,000
+So, basically if you want to import all the files
+
+208
+00:08:17,000 --> 00:08:19,000
+you can say star, okay?
+
+209
+00:08:19,000 --> 00:08:22,000
+So, that's how you can create a package in Java.
+
+210
+00:08:22,000 --> 00:08:24,000
+As I mentioned, you can create a folder inside a folder.
+
+211
+00:08:24,000 --> 00:08:27,000
+Example, let's say if I have a folder called other,
+
+212
+00:08:27,000 --> 00:08:29,000
+so let's say we have other folder.
+
+213
+00:08:29,000 --> 00:08:32,000
+And this tools actually belongs to other,
+
+214
+00:08:32,000 --> 00:08:34,000
+so now if I move this you can see
+
+215
+00:08:34,000 --> 00:08:36,000
+we have tools inside other.
+
+216
+00:08:36,000 --> 00:08:40,000
+Now, how it will look like when you talk about your Calc,
+
+217
+00:08:40,000 --> 00:08:43,000
+so you can see it says other.Calc.
+
+218
+00:08:43,000 --> 00:08:45,000
+So, you have to, if you want to go inside the package,
+
+219
+00:08:45,000 --> 00:08:48,000
+normally in folder structure we use slash, here we use dot.
+
+220
+00:08:48,000 --> 00:08:52,000
+So, it is other.tools.Calc, okay?
+
+221
+00:08:52,000 --> 00:08:54,000
+That's how you have to import it.
+
+222
+00:08:54,000 --> 00:08:57,000
+And of course you can say star, it will import everything.
+
+223
+00:08:57,000 --> 00:09:01,000
+Now, my question to you is if I say import other.*,
+
+224
+00:09:02,000 --> 00:09:07,000
+now is these two line same or can I remove this?
+
+225
+00:09:07,000 --> 00:09:09,000
+Of course, when you say star it should import everything.
+
+226
+00:09:09,000 --> 00:09:12,000
+But no, if you can see, it is giving you error.
+
+227
+00:09:12,000 --> 00:09:15,000
+The reason is when you say other.* it,
+
+228
+00:09:15,000 --> 00:09:18,000
+so star simply means all the files
+
+229
+00:09:18,000 --> 00:09:20,000
+not all the folders, okay?
+
+230
+00:09:20,000 --> 00:09:22,000
+So, in other if you have some files,
+
+231
+00:09:22,000 --> 00:09:24,000
+let's say if I create a new file here.
+
+232
+00:09:24,000 --> 00:09:25,000
+I will name this as A.java.
+
+233
+00:09:25,000 --> 00:09:28,000
+The moment you do that you can see this A class
+
+234
+00:09:28,000 --> 00:09:29,000
+belongs to other package.
+
+235
+00:09:29,000 --> 00:09:32,000
+Now you can easily use A but not Calc.
+
+236
+00:09:32,000 --> 00:09:37,000
+So, if you say A obj2 is equal to new A, this will work.
+
+237
+00:09:37,000 --> 00:09:40,000
+It's because you are saying other.*,
+
+238
+00:09:40,000 --> 00:09:41,000
+it will import all the classes,
+
+239
+00:09:41,000 --> 00:09:44,000
+which are all the files in the other folder,
+
+240
+00:09:44,000 --> 00:09:46,000
+not inside the folder, which is tools.
+
+241
+00:09:46,000 --> 00:09:49,000
+So, if you want other, I mean tools as well,
+
+242
+00:09:49,000 --> 00:09:52,000
+so you have to mention other.tools.*.
+
+243
+00:09:53,000 --> 00:09:55,000
+So, that's how basically you use a package structure.
+
+244
+00:09:55,000 --> 00:09:57,000
+Now, there's one thing you know,
+
+245
+00:09:57,000 --> 00:09:58,000
+not important at this point,
+
+246
+00:09:58,000 --> 00:10:01,000
+but since we're talking about package let's talk about it
+
+247
+00:10:01,000 --> 00:10:02,000
+because you will be seeing
+
+248
+00:10:02,000 --> 00:10:04,000
+those type of structure multiple times.
+
+249
+00:10:04,000 --> 00:10:06,000
+When you create a project, a big project,
+
+250
+00:10:06,000 --> 00:10:08,000
+normally you deploy your project
+
+251
+00:10:08,000 --> 00:10:10,000
+on the server somewhere, right?
+
+252
+00:10:10,000 --> 00:10:12,000
+And maybe you're creating a library, that's right.
+
+253
+00:10:12,000 --> 00:10:14,000
+What you do is when you create a project
+
+254
+00:10:14,000 --> 00:10:17,000
+it's not always for your use.
+
+255
+00:10:17,000 --> 00:10:18,000
+Sometime you create libraries
+
+256
+00:10:18,000 --> 00:10:20,000
+so that others can use your files.
+
+257
+00:10:20,000 --> 00:10:23,000
+Now, in this case as well you will create a package,
+
+258
+00:10:23,000 --> 00:10:26,000
+and then you will give your package to others.
+
+259
+00:10:26,000 --> 00:10:28,000
+The only thing is when you are sharing your package
+
+260
+00:10:28,000 --> 00:10:31,000
+to the entire world it should be unique,
+
+261
+00:10:31,000 --> 00:10:32,000
+it should have a unique name.
+
+262
+00:10:32,000 --> 00:10:33,000
+Let me show you something.
+
+263
+00:10:33,000 --> 00:10:35,000
+I will go to a website.
+
+264
+00:10:35,000 --> 00:10:36,000
+Now, this is one of the website
+
+265
+00:10:36,000 --> 00:10:39,000
+where you can get the libraries.
+
+266
+00:10:39,000 --> 00:10:42,000
+Now, library simply means if you want to do something,
+
+267
+00:10:42,000 --> 00:10:45,000
+and if you don't want to write the code entirely by yourself
+
+268
+00:10:45,000 --> 00:10:47,000
+you can use some libraries.
+
+269
+00:10:47,000 --> 00:10:49,000
+And most of the time we do that.
+
+270
+00:10:49,000 --> 00:10:51,000
+Example, let's say if I want to connect my application
+
+271
+00:10:51,000 --> 00:10:53,000
+with MongoDB, which is a database.
+
+272
+00:10:53,000 --> 00:10:55,000
+So, I can simply search for mongodb-driver-sync.
+
+273
+00:10:55,000 --> 00:10:58,000
+This is a driver which we use to connect Java with MongoDB.
+
+274
+00:10:58,000 --> 00:11:01,000
+So, you can use this package in your project.
+
+275
+00:11:01,000 --> 00:11:03,000
+Okay, let me select a version.
+
+276
+00:11:03,000 --> 00:11:07,000
+So, this is the package, okay?
+
+277
+00:11:07,000 --> 00:11:10,000
+Now, the thing is when we talk about this package
+
+278
+00:11:10,000 --> 00:11:11,000
+what should be name of it?
+
+279
+00:11:11,000 --> 00:11:14,000
+So, this name should be unique on the internet.
+
+280
+00:11:14,000 --> 00:11:16,000
+Now, how will you make something unique?
+
+281
+00:11:16,000 --> 00:11:17,000
+That's the tricky point, right?
+
+282
+00:11:17,000 --> 00:11:20,000
+So, when you are creating a project
+
+283
+00:11:20,000 --> 00:11:21,000
+how will you make it unique?
+
+284
+00:11:21,000 --> 00:11:24,000
+So, one way to do that is by reversing your domain name.
+
+285
+00:11:24,000 --> 00:11:24,000
+That's right.
+
+286
+00:11:24,000 --> 00:11:26,000
+Of course, right, when you're building a library
+
+287
+00:11:26,000 --> 00:11:29,000
+you will also have your website, your company website maybe.
+
+288
+00:11:29,000 --> 00:11:31,000
+So, let's say if we talk about a company like Google.
+
+289
+00:11:31,000 --> 00:11:34,000
+So, if I'm working for Google and if I'm creating a library,
+
+290
+00:11:34,000 --> 00:11:36,000
+so what I will do is I will name,
+
+291
+00:11:36,000 --> 00:11:38,000
+I will say this belongs to a package.
+
+292
+00:11:38,000 --> 00:11:41,000
+So, if I'm making a project for let's say Google
+
+293
+00:11:41,000 --> 00:11:44,000
+and I'm making a calculator or advanced calculator,
+
+294
+00:11:44,000 --> 00:11:49,000
+I will say com.google.calculation.
+
+295
+00:11:49,000 --> 00:11:50,000
+Now, this is my package name, okay?
+
+296
+00:11:50,000 --> 00:11:53,000
+So, by making com.google I'm making sure
+
+297
+00:11:53,000 --> 00:11:54,000
+it is unique, right?
+
+298
+00:11:54,000 --> 00:11:56,000
+Only Google can own this domain, right?
+
+299
+00:11:56,000 --> 00:11:57,000
+It's their domain.
+
+300
+00:11:57,000 --> 00:11:58,000
+So, that's how you do that.
+
+301
+00:11:58,000 --> 00:12:00,000
+So, depending upon your project
+
+302
+00:12:00,000 --> 00:12:01,000
+you will see these type of packages.
+
+303
+00:12:01,000 --> 00:12:04,000
+In fact, in future videos we will be using some packages
+
+304
+00:12:04,000 --> 00:12:06,000
+which have com. something.
+
+305
+00:12:06,000 --> 00:12:08,000
+It means they have just reverse the domain name
+
+306
+00:12:08,000 --> 00:12:09,000
+just to make it unique.
+
+307
+00:12:09,000 --> 00:12:10,000
+But again, for learning purpose
+
+308
+00:12:10,000 --> 00:12:12,000
+you can name your package anything you want.
+
+309
+00:12:12,000 --> 00:12:15,000
+Example, the way we are doing here, package other,
+
+310
+00:12:15,000 --> 00:12:17,000
+but it should have a meaning that's important.
+
+311
+00:12:17,000 --> 00:12:18,000
+So, yeah, that's about packages.
+
+312
+00:12:18,000 --> 00:12:20,000
+Don't worry, we'll use packages more.
+
+313
+00:12:20,000 --> 00:12:23,000
+In the upcoming videos it will make much more sense.
+
diff --git a/02 - Core Java/057 Source-code.url b/02 - Core Java/057 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/057 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/058 Access Modifiers_en.srt b/02 - Core Java/058 Access Modifiers_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..a9fc993d8b838780f523737e7ab652900f988a78
--- /dev/null
+++ b/02 - Core Java/058 Access Modifiers_en.srt	
@@ -0,0 +1,860 @@
+1
+00:00:00,000 --> 00:00:03,000
+(upbeat instrumental music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: Now once we talked about packages, it's a good time
+
+3
+00:00:05,000 --> 00:00:08,000
+to talk about access modifiers.
+
+4
+00:00:08,000 --> 00:00:09,000
+Now one of the access modifier we have seen,
+
+5
+00:00:09,000 --> 00:00:13,000
+in fact we have seen two, private and public.
+
+6
+00:00:13,000 --> 00:00:16,000
+Apart from this we have more, we have protected
+
+7
+00:00:16,000 --> 00:00:17,000
+and default as well.
+
+8
+00:00:17,000 --> 00:00:19,000
+So in this video let's try to explore them
+
+9
+00:00:19,000 --> 00:00:20,000
+or one or two videos.
+
+10
+00:00:20,000 --> 00:00:23,000
+So what I'll do is initially I will start with public.
+
+11
+00:00:23,000 --> 00:00:24,000
+Now what is public basically?
+
+12
+00:00:24,000 --> 00:00:25,000
+Let's go to demo
+
+13
+00:00:25,000 --> 00:00:28,000
+and we were trying to input the packages
+
+14
+00:00:28,000 --> 00:00:30,000
+and of course we should do that, right?
+
+15
+00:00:30,000 --> 00:00:31,000
+Anyway, we don't have to do that.
+
+16
+00:00:31,000 --> 00:00:33,000
+Java languages, it comes already.
+
+17
+00:00:33,000 --> 00:00:35,000
+So we don't have to worry about it.
+
+18
+00:00:35,000 --> 00:00:39,000
+And now what I will do is I will just go back to my class A.
+
+19
+00:00:39,000 --> 00:00:41,000
+Let's work with class A now.
+
+20
+00:00:41,000 --> 00:00:42,000
+And in this class A,
+
+21
+00:00:42,000 --> 00:00:45,000
+you can see the class A is public, okay?
+
+22
+00:00:45,000 --> 00:00:47,000
+And it belongs to a different package called other.
+
+23
+00:00:47,000 --> 00:00:52,000
+And in this class I will just create a variable called int,
+
+24
+00:00:52,000 --> 00:00:53,000
+let's say Marx.
+
+25
+00:00:53,000 --> 00:00:55,000
+So we have this variable called marks,
+
+26
+00:00:55,000 --> 00:00:56,000
+and the initial value for marks is six
+
+27
+00:00:56,000 --> 00:00:58,000
+because we just want to access this,
+
+28
+00:00:58,000 --> 00:00:59,000
+is it working or not?
+
+29
+00:00:59,000 --> 00:01:01,000
+Now how will you access this variable?
+
+30
+00:01:01,000 --> 00:01:03,000
+So you can just go back to demo.
+
+31
+00:01:03,000 --> 00:01:06,000
+So we have add, we have A, right, which has this code,
+
+32
+00:01:06,000 --> 00:01:07,000
+which is simple class.
+
+33
+00:01:07,000 --> 00:01:09,000
+And then we have our marks.
+
+34
+00:01:09,000 --> 00:01:10,000
+Let me go back to demo.
+
+35
+00:01:10,000 --> 00:01:12,000
+And in this, I want to access it.
+
+36
+00:01:12,000 --> 00:01:15,000
+So I will just remove all this lines, just want to work.
+
+37
+00:01:15,000 --> 00:01:17,000
+In fact, tools is also not a need now,
+
+38
+00:01:17,000 --> 00:01:19,000
+let's only work with other.
+
+39
+00:01:19,000 --> 00:01:21,000
+And in this, let me create a object of A.
+
+40
+00:01:21,000 --> 00:01:23,000
+Now can I create object of A?
+
+41
+00:01:23,000 --> 00:01:25,000
+Yes we can because we can access it.
+
+42
+00:01:25,000 --> 00:01:30,000
+And then I'm just trying to say obj.marks.
+
+43
+00:01:30,000 --> 00:01:31,000
+Now, trying to do that,
+
+44
+00:01:31,000 --> 00:01:33,000
+you can see it gives you an error.
+
+45
+00:01:33,000 --> 00:01:37,000
+It says, "The field A.marks is not visible."
+
+46
+00:01:37,000 --> 00:01:38,000
+I mean that's weird.
+
+47
+00:01:38,000 --> 00:01:39,000
+It's there, right?
+
+48
+00:01:39,000 --> 00:01:40,000
+Marks is there.
+
+49
+00:01:40,000 --> 00:01:42,000
+The thing is, it is not public.
+
+50
+00:01:42,000 --> 00:01:43,000
+Now, when it is not public,
+
+51
+00:01:43,000 --> 00:01:45,000
+you cannot access it outside the package.
+
+52
+00:01:45,000 --> 00:01:47,000
+You can see that's the issue we got.
+
+53
+00:01:47,000 --> 00:01:50,000
+Now what if you have a class in the same file
+
+54
+00:01:50,000 --> 00:01:54,000
+or maybe in the same package, let's say in the same package,
+
+55
+00:01:54,000 --> 00:01:55,000
+which is of demo,
+
+56
+00:01:55,000 --> 00:01:58,000
+I will create a file called B.java.
+
+57
+00:01:58,000 --> 00:02:01,000
+And in B.java, let me just say
+
+58
+00:02:01,000 --> 00:02:02,000
+because they're the same package now.
+
+59
+00:02:02,000 --> 00:02:05,000
+So no package is same package basically.
+
+60
+00:02:05,000 --> 00:02:10,000
+I will try to create a variable called int let's say marks.
+
+61
+00:02:10,000 --> 00:02:12,000
+Let's see if I can access this marks and demo.
+
+62
+00:02:12,000 --> 00:02:13,000
+I will just go back here
+
+63
+00:02:13,000 --> 00:02:16,000
+and I will repeat the same sentence, same line.
+
+64
+00:02:16,000 --> 00:02:20,000
+In fact, two, same statement with the help of B object now.
+
+65
+00:02:20,000 --> 00:02:21,000
+This is B.
+
+66
+00:02:21,000 --> 00:02:23,000
+The only thing is we have to use a different object name
+
+67
+00:02:23,000 --> 00:02:24,000
+because we cannot have same.
+
+68
+00:02:24,000 --> 00:02:27,000
+And using this OBJ can access marks.
+
+69
+00:02:27,000 --> 00:02:31,000
+So you see there is no issue, even if marks is not public,
+
+70
+00:02:31,000 --> 00:02:34,000
+it's no issue because they are in the same package.
+
+71
+00:02:34,000 --> 00:02:36,000
+The moment you have a different package
+
+72
+00:02:36,000 --> 00:02:39,000
+and if you don't mention public, it'll not work.
+
+73
+00:02:39,000 --> 00:02:40,000
+Okay, that's the issue.
+
+74
+00:02:40,000 --> 00:02:41,000
+You can see it is not working.
+
+75
+00:02:41,000 --> 00:02:44,000
+Now if you want something to be accessed
+
+76
+00:02:44,000 --> 00:02:47,000
+outside the package, always make it public.
+
+77
+00:02:47,000 --> 00:02:50,000
+And that's why methods, most of the time they're public,
+
+78
+00:02:50,000 --> 00:02:52,000
+variables should not be public.
+
+79
+00:02:52,000 --> 00:02:53,000
+But methods should be public.
+
+80
+00:02:53,000 --> 00:02:56,000
+Example, if I say public wide show here,
+
+81
+00:02:56,000 --> 00:02:58,000
+now show can, show is accessible.
+
+82
+00:02:58,000 --> 00:02:59,000
+I can use show from anywhere.
+
+83
+00:02:59,000 --> 00:03:04,000
+Example, if I can come back here obj.show,
+
+84
+00:03:04,000 --> 00:03:05,000
+this will work because that's public.
+
+85
+00:03:05,000 --> 00:03:08,000
+But if I don't write public there, it'll not work.
+
+86
+00:03:08,000 --> 00:03:09,000
+That's one.
+
+87
+00:03:09,000 --> 00:03:10,000
+So public means it can be
+
+88
+00:03:10,000 --> 00:03:12,000
+accessed from anywhere.
+
+89
+00:03:12,000 --> 00:03:13,000
+Okay?
+
+90
+00:03:13,000 --> 00:03:17,000
+Now apart from public, we also have private.
+
+91
+00:03:17,000 --> 00:03:21,000
+So if I talk about private, can I use private anywhere?
+
+92
+00:03:21,000 --> 00:03:24,000
+Private variable can be used in the same class
+
+93
+00:03:24,000 --> 00:03:25,000
+irrespective of the package.
+
+94
+00:03:25,000 --> 00:03:27,000
+Okay, package is the secondary part.
+
+95
+00:03:27,000 --> 00:03:31,000
+It can be used in the same class.
+
+96
+00:03:31,000 --> 00:03:34,000
+I can't even use outside the class, example,
+
+97
+00:03:34,000 --> 00:03:36,000
+let's say if you look at this B,
+
+98
+00:03:36,000 --> 00:03:37,000
+and if you look at this demo,
+
+99
+00:03:37,000 --> 00:03:39,000
+they're the same package, right?
+
+100
+00:03:39,000 --> 00:03:42,000
+But now if I create a private variable that here,
+
+101
+00:03:42,000 --> 00:03:44,000
+if I make this as a private variable,
+
+102
+00:03:45,000 --> 00:03:48,000
+which you should always mark your variables as private,
+
+103
+00:03:48,000 --> 00:03:49,000
+the moment you make it private,
+
+104
+00:03:49,000 --> 00:03:52,000
+even if they're the same package, you can't access it.
+
+105
+00:03:52,000 --> 00:03:55,000
+So private variables can be used in the same class
+
+106
+00:03:55,000 --> 00:03:57,000
+irrespective of the package.
+
+107
+00:03:57,000 --> 00:03:58,000
+It's on the same class.
+
+108
+00:03:58,000 --> 00:04:00,000
+Now let me reiterate, when you talk about public,
+
+109
+00:04:00,000 --> 00:04:03,000
+it can be used from anywhere, okay?
+
+110
+00:04:03,000 --> 00:04:06,000
+You can see this table, public can be used from anywhere.
+
+111
+00:04:06,000 --> 00:04:10,000
+Private can be used from the same class, okay?
+
+112
+00:04:10,000 --> 00:04:14,000
+Now apart from public and private, we have two more, okay?
+
+113
+00:04:14,000 --> 00:04:15,000
+Let's talk about those now.
+
+114
+00:04:15,000 --> 00:04:19,000
+Now if we talk about this A, if we don't mention private,
+
+115
+00:04:19,000 --> 00:04:21,000
+something should be applicable, right?
+
+116
+00:04:21,000 --> 00:04:24,000
+If it is not private, it's not public, what is it?
+
+117
+00:04:24,000 --> 00:04:28,000
+So by default there is something called a default
+
+118
+00:04:28,000 --> 00:04:29,000
+access modifier, okay?
+
+119
+00:04:29,000 --> 00:04:31,000
+Which is also called private protected,
+
+120
+00:04:31,000 --> 00:04:33,000
+but we'll talk about that later.
+
+121
+00:04:33,000 --> 00:04:35,000
+But it is called default.
+
+122
+00:04:35,000 --> 00:04:37,000
+The default simply means it can be accessed
+
+123
+00:04:37,000 --> 00:04:39,000
+in the same package.
+
+124
+00:04:39,000 --> 00:04:40,000
+It's as simple as that.
+
+125
+00:04:40,000 --> 00:04:42,000
+It can be accessed in the same package.
+
+126
+00:04:42,000 --> 00:04:43,000
+Example, if you talk about this B,
+
+127
+00:04:43,000 --> 00:04:45,000
+when private was not there, it was able
+
+128
+00:04:45,000 --> 00:04:48,000
+to be accessed in the same package.
+
+129
+00:04:48,000 --> 00:04:51,000
+So we got private, which can be accessed in the same class.
+
+130
+00:04:51,000 --> 00:04:54,000
+We got public, which can be accessed from anywhere.
+
+131
+00:04:54,000 --> 00:04:56,000
+And then we got private,
+
+132
+00:04:56,000 --> 00:04:58,000
+which can only be accessed in the same class
+
+133
+00:04:58,000 --> 00:05:00,000
+and default in the same package.
+
+134
+00:05:00,000 --> 00:05:03,000
+Okay, apart from this, we have one more,
+
+135
+00:05:03,000 --> 00:05:04,000
+which is called protected.
+
+136
+00:05:04,000 --> 00:05:06,000
+Now what is protected?
+
+137
+00:05:06,000 --> 00:05:08,000
+Now, let's say we have this class A,
+
+138
+00:05:08,000 --> 00:05:10,000
+which has, let's say if I make this variable
+
+139
+00:05:10,000 --> 00:05:12,000
+as protected, okay?
+
+140
+00:05:12,000 --> 00:05:15,000
+And then I'm going back to demo.
+
+141
+00:05:15,000 --> 00:05:17,000
+And inside this demo somewhere I'm creating a class
+
+142
+00:05:17,000 --> 00:05:18,000
+in the same package, basically,
+
+143
+00:05:18,000 --> 00:05:20,000
+it doesn't have to be in the same class
+
+144
+00:05:20,000 --> 00:05:23,000
+or same file, in a different package, basically.
+
+145
+00:05:23,000 --> 00:05:25,000
+Let me create class called C.
+
+146
+00:05:25,000 --> 00:05:27,000
+And then I'm saying
+
+147
+00:05:27,000 --> 00:05:32,000
+that this class extends A.
+
+148
+00:05:32,000 --> 00:05:35,000
+Now in this class A, so you can see this is protected.
+
+149
+00:05:35,000 --> 00:05:38,000
+Can I use protected in some other package,
+
+150
+00:05:39,000 --> 00:05:42,000
+you can see marks is protected in the other package
+
+151
+00:05:42,000 --> 00:05:43,000
+like demo
+
+152
+00:05:43,000 --> 00:05:44,000
+again, marks is not working.
+
+153
+00:05:44,000 --> 00:05:48,000
+So basically if you make it protected, you can't use it
+
+154
+00:05:48,000 --> 00:05:51,000
+outside the package, before coming there,
+
+155
+00:05:51,000 --> 00:05:53,000
+in fact, you know what we should do, let's try
+
+156
+00:05:53,000 --> 00:05:55,000
+to create a class here itself.
+
+157
+00:05:55,000 --> 00:05:58,000
+Let's say a class called launch.
+
+158
+00:05:58,000 --> 00:05:59,000
+And in this class,
+
+159
+00:05:59,000 --> 00:06:03,000
+let me have a method which is public wide, A, B, C,
+
+160
+00:06:03,000 --> 00:06:06,000
+let's say, and let me try to create object of A
+
+161
+00:06:06,000 --> 00:06:08,000
+equal to new A
+
+162
+00:06:08,000 --> 00:06:11,000
+and see from here, can I try, if I try to use marks,
+
+163
+00:06:11,000 --> 00:06:15,000
+let me just print marks obj.marks, okay?
+
+164
+00:06:15,000 --> 00:06:18,000
+It is working, so it works in the same package,
+
+165
+00:06:18,000 --> 00:06:20,000
+but it doesn't work in other packages.
+
+166
+00:06:20,000 --> 00:06:23,000
+Okay, so you can see demo is another package,
+
+167
+00:06:23,000 --> 00:06:25,000
+but what about a subclass?
+
+168
+00:06:25,000 --> 00:06:26,000
+We have class C here.
+
+169
+00:06:26,000 --> 00:06:31,000
+And then if I try to create a method, public void, A, B, C.
+
+170
+00:06:31,000 --> 00:06:33,000
+And you can see this class C looks same
+
+171
+00:06:33,000 --> 00:06:34,000
+in both the packages.
+
+172
+00:06:34,000 --> 00:06:36,000
+The difference is this is in different package
+
+173
+00:06:36,000 --> 00:06:37,000
+and it is extending A now.
+
+174
+00:06:37,000 --> 00:06:42,000
+And now if I try to access marks, it works.
+
+175
+00:06:42,000 --> 00:06:45,000
+There's no issue, you cannot access marks
+
+176
+00:06:45,000 --> 00:06:46,000
+outside the package,
+
+177
+00:06:46,000 --> 00:06:49,000
+but you can access marks outside the package,
+
+178
+00:06:49,000 --> 00:06:51,000
+but it should be a subclass.
+
+179
+00:06:51,000 --> 00:06:54,000
+If you can see C is a plus of A.
+
+180
+00:06:54,000 --> 00:06:56,000
+Now if you see this image here,
+
+181
+00:06:56,000 --> 00:06:58,000
+these is how our image looks like, right?
+
+182
+00:06:58,000 --> 00:07:01,000
+Let's talk about private, private can be used
+
+183
+00:07:01,000 --> 00:07:03,000
+in the same class, nowhere else.
+
+184
+00:07:04,000 --> 00:07:08,000
+Protected can be used in the same class,
+
+185
+00:07:08,000 --> 00:07:11,000
+in the same package, in the other package,
+
+186
+00:07:11,000 --> 00:07:12,000
+but subclass.
+
+187
+00:07:12,000 --> 00:07:15,000
+Public can be used everywhere.
+
+188
+00:07:16,000 --> 00:07:19,000
+Default can be used in the same package, okay?
+
+189
+00:07:19,000 --> 00:07:21,000
+It's that simple.
+
+190
+00:07:21,000 --> 00:07:23,000
+So this is how you specify the modifiers.
+
+191
+00:07:23,000 --> 00:07:26,000
+Now how do we use and which one to use?
+
+192
+00:07:26,000 --> 00:07:29,000
+Basically the idea is very simple.
+
+193
+00:07:29,000 --> 00:07:31,000
+Try to make your classes public, which we are doing.
+
+194
+00:07:31,000 --> 00:07:33,000
+And of course we don't have a public here.
+
+195
+00:07:33,000 --> 00:07:35,000
+The thing is, you can't even make this class public
+
+196
+00:07:35,000 --> 00:07:37,000
+because you cannot have two public classes
+
+197
+00:07:37,000 --> 00:07:39,000
+in the same file.
+
+198
+00:07:39,000 --> 00:07:42,000
+The general idea is in one file you should
+
+199
+00:07:42,000 --> 00:07:44,000
+have only one class.
+
+200
+00:07:44,000 --> 00:07:46,000
+So try to make your class public, next,
+
+201
+00:07:46,000 --> 00:07:50,000
+try to keep your variables, the instance variables private.
+
+202
+00:07:50,000 --> 00:07:53,000
+The methods most of the time will be public.
+
+203
+00:07:53,000 --> 00:07:54,000
+But if you think there is a method
+
+204
+00:07:54,000 --> 00:07:58,000
+or a variable which should be accessed only in the subclass
+
+205
+00:07:58,000 --> 00:08:01,000
+of other packages, use protected, try to avoid default.
+
+206
+00:08:01,000 --> 00:08:03,000
+Default is not something we should be using.
+
+207
+00:08:03,000 --> 00:08:06,000
+I know from, if you check all this thing,
+
+208
+00:08:06,000 --> 00:08:08,000
+we are promoting default a lot.
+
+209
+00:08:08,000 --> 00:08:10,000
+But don't do that, don't use default.
+
+210
+00:08:10,000 --> 00:08:12,000
+So for example, this is default.
+
+211
+00:08:12,000 --> 00:08:15,000
+Either make it private, public, protected or public.
+
+212
+00:08:15,000 --> 00:08:16,000
+Don't keep it default.
+
+213
+00:08:16,000 --> 00:08:17,000
+Default simply means you don't know
+
+214
+00:08:17,000 --> 00:08:19,000
+what to give the access.
+
+215
+00:08:19,000 --> 00:08:21,000
+So keep it private, protected or public.
+
diff --git a/02 - Core Java/058 Source-code.url b/02 - Core Java/058 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/058 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/059 Polymorphism_en.srt b/02 - Core Java/059 Polymorphism_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..fc0a5046b651c24f4a89431fb9cde6227a939a60
--- /dev/null
+++ b/02 - Core Java/059 Polymorphism_en.srt	
@@ -0,0 +1,400 @@
+1
+00:00:00,000 --> 00:00:03,000
+(light calming music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, let's talk about polymorphism.
+
+3
+00:00:06,000 --> 00:00:08,000
+Remember we have talked about method overriding,
+
+4
+00:00:08,000 --> 00:00:10,000
+and then we say there's something more?
+
+5
+00:00:10,000 --> 00:00:11,000
+This is where we are talking about.
+
+6
+00:00:11,000 --> 00:00:15,000
+So we have a concept of polymorphism.
+
+7
+00:00:15,000 --> 00:00:18,000
+Now this is a very important concept in terms of OOPs
+
+8
+00:00:18,000 --> 00:00:20,000
+and most of the languages which implements OOPs
+
+9
+00:00:20,000 --> 00:00:21,000
+has this concept.
+
+10
+00:00:21,000 --> 00:00:23,000
+Now, what is polymorphism?
+
+11
+00:00:23,000 --> 00:00:26,000
+Now basically as a concept, it has two words.
+
+12
+00:00:26,000 --> 00:00:28,000
+One is poly, second is morphism.
+
+13
+00:00:28,000 --> 00:00:33,000
+Now poly simply means many, and morphism means behavior.
+
+14
+00:00:34,000 --> 00:00:36,000
+Now what it means is there's something which behaves
+
+15
+00:00:36,000 --> 00:00:40,000
+differently in different situatio based on situation.
+
+16
+00:00:40,000 --> 00:00:41,000
+Let's say as a human,
+
+17
+00:00:41,000 --> 00:00:44,000
+you behave differently at different locations, right?
+
+18
+00:00:44,000 --> 00:00:48,000
+Example, for at home, I behave differently.
+
+19
+00:00:48,000 --> 00:00:49,000
+At my office, I behave differently.
+
+20
+00:00:49,000 --> 00:00:52,000
+When I'm with my friends, I behave differently, right?
+
+21
+00:00:52,000 --> 00:00:54,000
+So that situation changes me in the same way
+
+22
+00:00:54,000 --> 00:00:55,000
+because the name also changes right?
+
+23
+00:00:55,000 --> 00:01:00,000
+At home, I'm a son, husband, a father,
+
+24
+00:01:00,000 --> 00:01:04,000
+at office, I'm a colleague, I'm a boss, I'm an employee,
+
+25
+00:01:05,000 --> 00:01:06,000
+with my friends, okay?
+
+26
+00:01:06,000 --> 00:01:09,000
+They use different words, but then let's not mention that.
+
+27
+00:01:09,000 --> 00:01:11,000
+So the important thing is your behavior,
+
+28
+00:01:11,000 --> 00:01:12,000
+your name changes at every place, right?
+
+29
+00:01:12,000 --> 00:01:14,000
+Your behavior changes based on that.
+
+30
+00:01:14,000 --> 00:01:17,000
+In the same way in the world of object oriented,
+
+31
+00:01:17,000 --> 00:01:19,000
+we have a concept of many behavior, polymorphism.
+
+32
+00:01:19,000 --> 00:01:22,000
+So the same object or the same reference
+
+33
+00:01:22,000 --> 00:01:24,000
+will have different behavior
+
+34
+00:01:24,000 --> 00:01:26,000
+based on how you create the instance of it.
+
+35
+00:01:26,000 --> 00:01:28,000
+Now, to implement this,
+
+36
+00:01:28,000 --> 00:01:30,000
+there are multiple ways in different languages.
+
+37
+00:01:30,000 --> 00:01:32,000
+But before we go into the implementation,
+
+38
+00:01:32,000 --> 00:01:34,000
+let's talk about its type.
+
+39
+00:01:34,000 --> 00:01:36,000
+So there are two types of polymorphism.
+
+40
+00:01:36,000 --> 00:01:40,000
+One is called a compile time polymorphism,
+
+41
+00:01:40,000 --> 00:01:43,000
+and second is called a runtime polymorphism.
+
+42
+00:01:43,000 --> 00:01:44,000
+Of course, they have different names.
+
+43
+00:01:44,000 --> 00:01:47,000
+Compile time is also called early binding,
+
+44
+00:01:47,000 --> 00:01:49,000
+runtime polymorphism also called late binding.
+
+45
+00:01:49,000 --> 00:01:53,000
+But we have these two words, compile time and run time.
+
+46
+00:01:53,000 --> 00:01:54,000
+Now what do you mean by compile time?
+
+47
+00:01:54,000 --> 00:01:56,000
+See if you can define your behavior.
+
+48
+00:01:56,000 --> 00:01:59,000
+So the behavior is defined at compile time,
+
+49
+00:01:59,000 --> 00:02:01,000
+that is compile time polymorphism.
+
+50
+00:02:01,000 --> 00:02:03,000
+If the behavior will be defined at run time,
+
+51
+00:02:03,000 --> 00:02:06,000
+that is called a run time polymorphism.
+
+52
+00:02:06,000 --> 00:02:07,000
+So when you compile the file
+
+53
+00:02:07,000 --> 00:02:11,000
+and when you know what thing will get executed
+
+54
+00:02:11,000 --> 00:02:13,000
+at the compile time itself, it is compile time.
+
+55
+00:02:13,000 --> 00:02:15,000
+Now, which method will be executed,
+
+56
+00:02:15,000 --> 00:02:17,000
+will be decided at run time, that's run time.
+
+57
+00:02:17,000 --> 00:02:20,000
+Now we have done two examples here,
+
+58
+00:02:20,000 --> 00:02:23,000
+which is overloading and overriding.
+
+59
+00:02:23,000 --> 00:02:25,000
+So if you talk about overloading,
+
+60
+00:02:25,000 --> 00:02:26,000
+it's a part of compile time
+
+61
+00:02:26,000 --> 00:02:28,000
+because at the compile time itself,
+
+62
+00:02:28,000 --> 00:02:30,000
+example, let's say if you have two methods,
+
+63
+00:02:30,000 --> 00:02:32,000
+you have, let's say two methods,
+
+64
+00:02:32,000 --> 00:02:37,000
+which is add, which takes two parameters, int and int.
+
+65
+00:02:38,000 --> 00:02:40,000
+And then we have one more method here, which is add.
+
+66
+00:02:40,000 --> 00:02:43,000
+And when you say int, int, int,
+
+67
+00:02:43,000 --> 00:02:45,000
+which takes three parameters.
+
+68
+00:02:45,000 --> 00:02:48,000
+Now both this have the same name, but different parameters.
+
+69
+00:02:48,000 --> 00:02:50,000
+That is method overloading.
+
+70
+00:02:50,000 --> 00:02:51,000
+Now, which method to execute?
+
+71
+00:02:51,000 --> 00:02:53,000
+Will you execute the first or second method
+
+72
+00:02:53,000 --> 00:02:55,000
+will be decided at compile time.
+
+73
+00:02:55,000 --> 00:02:56,000
+Now, let's say you have two classes,
+
+74
+00:02:56,000 --> 00:02:59,000
+class A and class B to add two different classes.
+
+75
+00:02:59,000 --> 00:03:02,000
+And class B extends class A.
+
+76
+00:03:02,000 --> 00:03:05,000
+We have talked about this in method overriding.
+
+77
+00:03:05,000 --> 00:03:07,000
+And let's say you have a method which is add,
+
+78
+00:03:07,000 --> 00:03:08,000
+which takes two parameters.
+
+79
+00:03:08,000 --> 00:03:11,000
+And also here we also have the add method,
+
+80
+00:03:11,000 --> 00:03:13,000
+which takes two parameters.
+
+81
+00:03:13,000 --> 00:03:16,000
+Now, out of these two, which one will get executed,
+
+82
+00:03:16,000 --> 00:03:18,000
+it will be decided at run time.
+
+83
+00:03:18,000 --> 00:03:20,000
+So that is called run time polymorphism.
+
+84
+00:03:20,000 --> 00:03:21,000
+In fact, there's one more concept
+
+85
+00:03:21,000 --> 00:03:24,000
+which we're going to discuss in the implementation
+
+86
+00:03:24,000 --> 00:03:26,000
+when we talk about dynamic method dispatch,
+
+87
+00:03:26,000 --> 00:03:28,000
+at that point, this thing will get more clear.
+
+88
+00:03:28,000 --> 00:03:30,000
+But just to generalize, what is polymorphism?
+
+89
+00:03:30,000 --> 00:03:32,000
+Polymorphism means many behavior.
+
+90
+00:03:32,000 --> 00:03:35,000
+So your behavior of your reference
+
+91
+00:03:35,000 --> 00:03:38,000
+or your execution will change based on some situation.
+
+92
+00:03:38,000 --> 00:03:42,000
+If it is compile time, which is your method overloading,
+
+93
+00:03:42,000 --> 00:03:43,000
+where you decide
+
+94
+00:03:43,000 --> 00:03:45,000
+based on the parameters at compile time itself,
+
+95
+00:03:45,000 --> 00:03:48,000
+in runtime, you're not sure which method will be called
+
+96
+00:03:48,000 --> 00:03:50,000
+because both the methods have the same name,
+
+97
+00:03:50,000 --> 00:03:53,000
+same parameters, something which will decide that
+
+98
+00:03:53,000 --> 00:03:54,000
+we'll discuss in the next video.
+
+99
+00:03:54,000 --> 00:03:56,000
+But that is method overriding,
+
+100
+00:03:56,000 --> 00:03:58,000
+which is run time polymorphism.
+
diff --git a/02 - Core Java/059 Source-code.url b/02 - Core Java/059 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/059 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/060 Dynamic Method Dispatch_en.srt b/02 - Core Java/060 Dynamic Method Dispatch_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..e57654a45249c19b7109abc66b430ef388fc5b00
--- /dev/null
+++ b/02 - Core Java/060 Dynamic Method Dispatch_en.srt	
@@ -0,0 +1,792 @@
+1
+00:00:00,000 --> 00:00:03,000
+(gentle piano music)
+
+2
+00:00:03,000 --> 00:00:04,000
+-: Now in this video,
+
+3
+00:00:04,000 --> 00:00:07,000
+let's talk about dynamic method dispatch.
+
+4
+00:00:07,000 --> 00:00:09,000
+Now, once we have went through what is polymorphism,
+
+5
+00:00:09,000 --> 00:00:11,000
+we have also mentioned that it is same thing,
+
+6
+00:00:11,000 --> 00:00:12,000
+multiple behavior,
+
+7
+00:00:12,000 --> 00:00:15,000
+and we have two types of polymorphism,
+
+8
+00:00:15,000 --> 00:00:18,000
+which is compile time polymorphism run time polymorphism.
+
+9
+00:00:18,000 --> 00:00:20,000
+Now to implement run time polymorphism,
+
+10
+00:00:20,000 --> 00:00:22,000
+let's try one more example here.
+
+11
+00:00:22,000 --> 00:00:26,000
+And we do that with the help of dynamic method dispatch.
+
+12
+00:00:26,000 --> 00:00:28,000
+Again, to keep it simple, we'll use a simple class
+
+13
+00:00:28,000 --> 00:00:31,000
+like class A and then we got class B.
+
+14
+00:00:31,000 --> 00:00:34,000
+And let's say class B extends class A.
+
+15
+00:00:34,000 --> 00:00:37,000
+Okay, and let's say we have class C.
+
+16
+00:00:37,000 --> 00:00:39,000
+And again, we have discussed most of the topics.
+
+17
+00:00:39,000 --> 00:00:43,000
+So let's make it quick. So we got class C.
+
+18
+00:00:43,000 --> 00:00:45,000
+So if you can see we have class A,
+
+19
+00:00:45,000 --> 00:00:48,000
+which is getting extended by B and C both.
+
+20
+00:00:48,000 --> 00:00:51,000
+So you can say class A is parent,
+
+21
+00:00:51,000 --> 00:00:54,000
+and we have two child there, one is B and one is C.
+
+22
+00:00:54,000 --> 00:00:56,000
+Now what we'll do is, in this A,
+
+23
+00:00:56,000 --> 00:00:59,000
+I will create public white show,
+
+24
+00:00:59,000 --> 00:01:02,000
+okay, and this show will print,
+
+25
+00:01:02,000 --> 00:01:04,000
+let's say in A show.
+
+26
+00:01:04,000 --> 00:01:07,000
+Okay, and we'll be using classy, but later.
+
+27
+00:01:07,000 --> 00:01:11,000
+As of now, let's only focus on class A and class B.
+
+28
+00:01:11,000 --> 00:01:14,000
+Now, my question to everyone is, I mean, okay,
+
+29
+00:01:14,000 --> 00:01:16,000
+let's remove this class A just to remove the confusion.
+
+30
+00:01:16,000 --> 00:01:17,000
+Let's go step by step.
+
+31
+00:01:17,000 --> 00:01:18,000
+So let's say we have these two classes,
+
+32
+00:01:18,000 --> 00:01:20,000
+class B extends class A.
+
+33
+00:01:20,000 --> 00:01:22,000
+Now my question to you is,
+
+34
+00:01:22,000 --> 00:01:24,000
+how do I create an object of class B?
+
+35
+00:01:24,000 --> 00:01:26,000
+And of course we have talked about this from a long time.
+
+36
+00:01:26,000 --> 00:01:29,000
+I can say we B obj equal to new B,
+
+37
+00:01:29,000 --> 00:01:31,000
+and that's how you get the object, right?
+
+38
+00:01:31,000 --> 00:01:32,000
+And of course, using this OBJ,
+
+39
+00:01:32,000 --> 00:01:35,000
+I can call show there's no harm.
+
+40
+00:01:35,000 --> 00:01:39,000
+Compile this code and run. You can see we got in A show.
+
+41
+00:01:39,000 --> 00:01:41,000
+Now this is how you create the object right?
+
+42
+00:01:41,000 --> 00:01:43,000
+Now there is one more thing.
+
+43
+00:01:43,000 --> 00:01:47,000
+Can I create a reference of A, an object of B?
+
+44
+00:01:47,000 --> 00:01:48,000
+Is it possible?
+
+45
+00:01:48,000 --> 00:01:49,000
+Since B
+
+46
+00:01:49,000 --> 00:01:50,000
+extends A.
+
+47
+00:01:50,000 --> 00:01:53,000
+So you can say B is a child of A.
+
+48
+00:01:53,000 --> 00:01:56,000
+So can I refer this OBJ as A?
+
+49
+00:01:56,000 --> 00:01:58,000
+And the object is B.
+
+50
+00:01:58,000 --> 00:02:00,000
+Now when you look at this OBJ, what is this OBJ?
+
+51
+00:02:00,000 --> 00:02:03,000
+It's a variable, right? And what is a type of a variable?
+
+52
+00:02:03,000 --> 00:02:06,000
+The type is A here, right?
+
+53
+00:02:06,000 --> 00:02:10,000
+So the OBJ type is A, but the implementation is B.
+
+54
+00:02:10,000 --> 00:02:12,000
+Okay, that's the point remember.
+
+55
+00:02:12,000 --> 00:02:13,000
+And this perfectly works.
+
+56
+00:02:13,000 --> 00:02:15,000
+Now if you want to imagine this,
+
+57
+00:02:15,000 --> 00:02:17,000
+let's go with this one example here,
+
+58
+00:02:17,000 --> 00:02:18,000
+which I will write here.
+
+59
+00:02:18,000 --> 00:02:20,000
+Let's say if I create a class called computer,
+
+60
+00:02:20,000 --> 00:02:23,000
+and of course class computer has some methods, okay?
+
+61
+00:02:23,000 --> 00:02:25,000
+And then class, laptop.
+
+62
+00:02:25,000 --> 00:02:28,000
+And we all know that laptop is a computer.
+
+63
+00:02:28,000 --> 00:02:31,000
+So I can also say laptop extends computer.
+
+64
+00:02:31,000 --> 00:02:33,000
+Yeah, we can say that, right?
+
+65
+00:02:33,000 --> 00:02:34,000
+And now
+
+66
+00:02:34,000 --> 00:02:36,000
+if I say laptop is a computer,
+
+67
+00:02:36,000 --> 00:02:39,000
+if I want to create object of a laptop,
+
+68
+00:02:39,000 --> 00:02:40,000
+of course I will do it.
+
+69
+00:02:40,000 --> 00:02:42,000
+It's very simple. You will say laptop.
+
+70
+00:02:42,000 --> 00:02:45,000
+Let's say lap is equal to new laptop.
+
+71
+00:02:45,000 --> 00:02:48,000
+So let's say, instead of saying a lap, you say OBJ 1,
+
+72
+00:02:48,000 --> 00:02:51,000
+and then I can just call all the methods.
+
+73
+00:02:51,000 --> 00:02:54,000
+But my question is can I refer this OBJ 1 as laptop?
+
+74
+00:02:54,000 --> 00:02:55,000
+Yes, it is a type of laptop,
+
+75
+00:02:55,000 --> 00:02:57,000
+and I can also say this is a computer.
+
+76
+00:02:57,000 --> 00:02:59,000
+And that's what you do, right? When you look at the laptop,
+
+77
+00:02:59,000 --> 00:03:01,000
+you can say, hey, that is a laptop,
+
+78
+00:03:01,000 --> 00:03:03,000
+but that's also a computer.
+
+79
+00:03:03,000 --> 00:03:05,000
+We are referring that as a computer.
+
+80
+00:03:05,000 --> 00:03:08,000
+So we are referring this OBJ, which is an object,
+
+81
+00:03:08,000 --> 00:03:12,000
+as a computer, but technically it's a laptop, right?
+
+82
+00:03:12,000 --> 00:03:16,000
+In the same way we can refer this OBJ of type A.
+
+83
+00:03:16,000 --> 00:03:20,000
+So we can mention the type as parent,
+
+84
+00:03:20,000 --> 00:03:22,000
+but the object can be of child, okay?
+
+85
+00:03:22,000 --> 00:03:24,000
+So I've just created this laptop computer
+
+86
+00:03:24,000 --> 00:03:26,000
+just to show you, let me remove that.
+
+87
+00:03:26,000 --> 00:03:30,000
+So yet it is possible to create a reference of a super class
+
+88
+00:03:30,000 --> 00:03:32,000
+and the object of a subclass.
+
+89
+00:03:32,000 --> 00:03:35,000
+Okay, and this will surely work.
+
+90
+00:03:35,000 --> 00:03:36,000
+Let's compile, there's no issue.
+
+91
+00:03:36,000 --> 00:03:39,000
+Let's run. And you can see it says in A show.
+
+92
+00:03:40,000 --> 00:03:43,000
+But the twist is, if I have the same method,
+
+93
+00:03:43,000 --> 00:03:46,000
+and we have talked about this in method overriding,
+
+94
+00:03:46,000 --> 00:03:48,000
+if I have the same method,
+
+95
+00:03:48,000 --> 00:03:50,000
+and if I say this is in B show,
+
+96
+00:03:50,000 --> 00:03:52,000
+now what it will call?
+
+97
+00:03:52,000 --> 00:03:54,000
+Will it call in A show or in B show?
+
+98
+00:03:54,000 --> 00:03:57,000
+As per the method overriding, it should call in B show.
+
+99
+00:03:57,000 --> 00:04:02,000
+But look at reference. Reference is of type A.
+
+100
+00:04:02,000 --> 00:04:04,000
+That's tricky, right? Let's try,
+
+101
+00:04:04,000 --> 00:04:05,000
+in fact, what I will do now,
+
+102
+00:04:05,000 --> 00:04:07,000
+just to first let's run this call
+
+103
+00:04:07,000 --> 00:04:09,000
+and I will show you something.
+
+104
+00:04:09,000 --> 00:04:11,000
+You can see it says in B show.
+
+105
+00:04:11,000 --> 00:04:14,000
+Let me initially set the object of A itself.
+
+106
+00:04:14,000 --> 00:04:16,000
+And then let's go step by step.
+
+107
+00:04:16,000 --> 00:04:18,000
+So I will say compile and run.
+
+108
+00:04:18,000 --> 00:04:19,000
+It says in A show,
+
+109
+00:04:19,000 --> 00:04:22,000
+in fact I can call this OBJ show once more,
+
+110
+00:04:22,000 --> 00:04:23,000
+but before calling OBJ show,
+
+111
+00:04:23,000 --> 00:04:26,000
+what I will do is I will make one change here.
+
+112
+00:04:27,000 --> 00:04:28,000
+I can just come back here and I can say
+
+113
+00:04:28,000 --> 00:04:30,000
+OBJ is equal to new B. That's right.
+
+114
+00:04:30,000 --> 00:04:33,000
+We can assign a new object to the old variable.
+
+115
+00:04:33,000 --> 00:04:36,000
+Okay? Now if you want to understand this with a memory,
+
+116
+00:04:36,000 --> 00:04:39,000
+of course we have a stack here, right?
+
+117
+00:04:39,000 --> 00:04:40,000
+In this stack we have different variables.
+
+118
+00:04:40,000 --> 00:04:43,000
+And then we have a heap memory here.
+
+119
+00:04:43,000 --> 00:04:46,000
+Now initially when you say OBJ, that's your object, right?
+
+120
+00:04:46,000 --> 00:04:48,000
+And it will create object of A.
+
+121
+00:04:48,000 --> 00:04:50,000
+So 1 0 1 is object of A,
+
+122
+00:04:50,000 --> 00:04:52,000
+I'm talking about line number 24.
+
+123
+00:04:52,000 --> 00:04:55,000
+Okay, line number 24, we have this line.
+
+124
+00:04:55,000 --> 00:04:58,000
+So that's an object here and it will have some methods.
+
+125
+00:04:58,000 --> 00:05:00,000
+The method name is show itself, right?
+
+126
+00:05:00,000 --> 00:05:02,000
+And this will have a value which is 1 0 1.
+
+127
+00:05:02,000 --> 00:05:05,000
+So I'm talking about line number 24, okay?
+
+128
+00:05:05,000 --> 00:05:07,000
+On 24, this is a link.
+
+129
+00:05:07,000 --> 00:05:10,000
+Now when you say obj.show, line number 25 obj.show.
+
+130
+00:05:10,000 --> 00:05:12,000
+At that point it will look.
+
+131
+00:05:12,000 --> 00:05:15,000
+Okay, so obj.show, that means I have to call the show method
+
+132
+00:05:15,000 --> 00:05:16,000
+of object A.
+
+133
+00:05:16,000 --> 00:05:18,000
+So this my friend is an object of A.
+
+134
+00:05:19,000 --> 00:05:22,000
+And now on line number 28, we made some changes.
+
+135
+00:05:22,000 --> 00:05:25,000
+That is now this particular object
+
+136
+00:05:25,000 --> 00:05:26,000
+is referring to the object of B.
+
+137
+00:05:26,000 --> 00:05:30,000
+So we got one more object here, which is let's say 1 0 3,
+
+138
+00:05:31,000 --> 00:05:33,000
+and this is an object of B now.
+
+139
+00:05:33,000 --> 00:05:35,000
+Okay, this will also have a show method
+
+140
+00:05:35,000 --> 00:05:37,000
+because that is what we mentioned there.
+
+141
+00:05:37,000 --> 00:05:41,000
+And now since we are changing the value here,
+
+142
+00:05:41,000 --> 00:05:43,000
+this will be replaced by 1 0 3.
+
+143
+00:05:43,000 --> 00:05:45,000
+There's no 1 0 1 anymore.
+
+144
+00:05:45,000 --> 00:05:49,000
+That means this link is broken and we got a new link.
+
+145
+00:05:49,000 --> 00:05:52,000
+Now on line number 29, when you say obj.show,
+
+146
+00:05:52,000 --> 00:05:55,000
+it will call the show method of B.
+
+147
+00:05:55,000 --> 00:05:59,000
+So it's not about what is a type of the object or reference.
+
+148
+00:05:59,000 --> 00:06:03,000
+You can say type is still A, but the object is B.
+
+149
+00:06:03,000 --> 00:06:05,000
+And that's what you call the B show.
+
+150
+00:06:05,000 --> 00:06:08,000
+Let me compile and run.
+
+151
+00:06:08,000 --> 00:06:11,000
+You can see at first for this line, it is printing in A show
+
+152
+00:06:11,000 --> 00:06:14,000
+for this line is printing in B show.
+
+153
+00:06:14,000 --> 00:06:17,000
+Likewise, if I create another class here, class C,
+
+154
+00:06:17,000 --> 00:06:19,000
+which extends A,
+
+155
+00:06:19,000 --> 00:06:20,000
+and if I have the same method,
+
+156
+00:06:20,000 --> 00:06:23,000
+I will just reuse my own code.
+
+157
+00:06:23,000 --> 00:06:26,000
+And if I say this is in C show,
+
+158
+00:06:26,000 --> 00:06:29,000
+what will happen if I create, if I just go back here
+
+159
+00:06:29,000 --> 00:06:32,000
+and say OBJ equal to new C.
+
+160
+00:06:32,000 --> 00:06:34,000
+And if I say obj.show, what do you think?
+
+161
+00:06:34,000 --> 00:06:36,000
+What will happen if I run the for the third time?
+
+162
+00:06:36,000 --> 00:06:38,000
+And that of course right,
+
+163
+00:06:38,000 --> 00:06:40,000
+different object will have a different behavior.
+
+164
+00:06:40,000 --> 00:06:42,000
+Remember run time polymorphism
+
+165
+00:06:42,000 --> 00:06:44,000
+and you can see we got in C show.
+
+166
+00:06:44,000 --> 00:06:46,000
+So the same object, which is obj.show
+
+167
+00:06:46,000 --> 00:06:49,000
+is behaving differently with different objects.
+
+168
+00:06:49,000 --> 00:06:50,000
+Polymorphism, right?
+
+169
+00:06:50,000 --> 00:06:53,000
+So if you say obj.show, we are not even sure.
+
+170
+00:06:53,000 --> 00:06:56,000
+So when you compile this code, at that point we are not sure
+
+171
+00:06:56,000 --> 00:06:59,000
+obj.show will call which method of which class,
+
+172
+00:06:59,000 --> 00:07:02,000
+I mean method of which class, it'll be decided at run time.
+
+173
+00:07:02,000 --> 00:07:05,000
+And that's what is called run time of polymorphism.
+
+174
+00:07:05,000 --> 00:07:10,000
+And all this concept is called dynamic method dispatch,
+
+175
+00:07:10,000 --> 00:07:11,000
+because that's dynamic.
+
+176
+00:07:11,000 --> 00:07:13,000
+Which method will it will call? We are not sure.
+
+177
+00:07:13,000 --> 00:07:15,000
+Okay, and that's how it works.
+
+178
+00:07:15,000 --> 00:07:17,000
+So point to remember here is,
+
+179
+00:07:17,000 --> 00:07:20,000
+in respect you of what type of object you have
+
+180
+00:07:20,000 --> 00:07:24,000
+or what type of variable you create. It's of type A,
+
+181
+00:07:24,000 --> 00:07:27,000
+but it all depends upon what object you have.
+
+182
+00:07:27,000 --> 00:07:29,000
+Right, it is only possible when you have inheritance. Okay?
+
+183
+00:07:29,000 --> 00:07:33,000
+You can't simply say we are getting a new class, class D,
+
+184
+00:07:33,000 --> 00:07:37,000
+and you will say, okay, not demo, class D.
+
+185
+00:07:37,000 --> 00:07:39,000
+And you can't simply go back here and say
+
+186
+00:07:39,000 --> 00:07:43,000
+OBJ equal to new D, this will not work
+
+187
+00:07:43,000 --> 00:07:45,000
+because D is not extending A.
+
+188
+00:07:45,000 --> 00:07:47,000
+If you can see, where if you can verify
+
+189
+00:07:47,000 --> 00:07:49,000
+D is not extending A.
+
+190
+00:07:49,000 --> 00:07:50,000
+So this will not work.
+
+191
+00:07:50,000 --> 00:07:53,000
+This will only work when you have inheritance.
+
+192
+00:07:53,000 --> 00:07:56,000
+So only you can have a child objects
+
+193
+00:07:56,000 --> 00:07:58,000
+for the parent
+
+194
+00:07:58,000 --> 00:07:59,000
+variable,
+
+195
+00:07:59,000 --> 00:08:01,000
+which is A OBJ, parent type variable.
+
+196
+00:08:01,000 --> 00:08:03,000
+So yeah, that's it from this video where we talked about
+
+197
+00:08:03,000 --> 00:08:04,000
+dynamic method dispatch,
+
+198
+00:08:04,000 --> 00:08:06,000
+which is other run time polymorphism.
+
diff --git a/02 - Core Java/060 Source-code.url b/02 - Core Java/060 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/060 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/061 Final keyword_en.srt b/02 - Core Java/061 Final keyword_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..c9a40ab89927985d47b3a1d1d7bfdbba3ab0fbce
--- /dev/null
+++ b/02 - Core Java/061 Final keyword_en.srt	
@@ -0,0 +1,616 @@
+1
+00:00:00,000 --> 00:00:03,000
+(peaceful piano tones ring)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, let's talk about final keyword.
+
+3
+00:00:06,000 --> 00:00:09,000
+Okay, so the keyword we are talking about now is final.
+
+4
+00:00:09,000 --> 00:00:13,000
+Now basically, final keyword can be used with a variable,
+
+5
+00:00:13,000 --> 00:00:16,000
+a final keyword can be used with a method,
+
+6
+00:00:16,000 --> 00:00:18,000
+and a final keyword can be used with a class
+
+7
+00:00:18,000 --> 00:00:20,000
+and we'll go step by step.
+
+8
+00:00:20,000 --> 00:00:23,000
+So let's start with the final with variable.
+
+9
+00:00:23,000 --> 00:00:25,000
+Now, when you make a variable,
+
+10
+00:00:25,000 --> 00:00:27,000
+let's say if I create a variable called num,
+
+11
+00:00:27,000 --> 00:00:30,000
+and if I say the value for num is eight.
+
+12
+00:00:30,000 --> 00:00:32,000
+And of course when you make a variable,
+
+13
+00:00:32,000 --> 00:00:34,000
+of course you can change the valuator, right?
+
+14
+00:00:34,000 --> 00:00:35,000
+So initially the value was eight
+
+15
+00:00:35,000 --> 00:00:37,000
+and now you're making it nine.
+
+16
+00:00:37,000 --> 00:00:38,000
+There's no problem, right?
+
+17
+00:00:38,000 --> 00:00:40,000
+And of course you can print the value as well.
+
+18
+00:00:40,000 --> 00:00:44,000
+So if I compile this code and execute,
+
+19
+00:00:44,000 --> 00:00:45,000
+the recent value is nine.
+
+20
+00:00:45,000 --> 00:00:47,000
+Now there's a concept of making constants, right?
+
+21
+00:00:47,000 --> 00:00:48,000
+So what is constant?
+
+22
+00:00:48,000 --> 00:00:50,000
+So if you make your variable constant,
+
+23
+00:00:50,000 --> 00:00:53,000
+you can't change the value of it.
+
+24
+00:00:53,000 --> 00:00:56,000
+Now the way you can do that is by using a final keyword.
+
+25
+00:00:56,000 --> 00:00:59,000
+Now, in different languages, we use different keywords.
+
+26
+00:00:59,000 --> 00:01:03,000
+I guess in C++, we use const. In Java we say final.
+
+27
+00:01:03,000 --> 00:01:07,000
+So the moment you make your variable as final variable,
+
+28
+00:01:07,000 --> 00:01:09,000
+the variable becomes constant.
+
+29
+00:01:09,000 --> 00:01:13,000
+So once you assign the value, you can't change it.
+
+30
+00:01:13,000 --> 00:01:14,000
+Okay, that's important.
+
+31
+00:01:14,000 --> 00:01:16,000
+And that's why you can see we've got an error here.
+
+32
+00:01:16,000 --> 00:01:18,000
+In fact, you can also get this error by compiling the code.
+
+33
+00:01:18,000 --> 00:01:21,000
+You can see it says, "Cannot assign a value
+
+34
+00:01:21,000 --> 00:01:23,000
+to a final variable."
+
+35
+00:01:23,000 --> 00:01:27,000
+So that's final, yeah, "final variable num."
+
+36
+00:01:27,000 --> 00:01:30,000
+So because num is final, you can't change the value.
+
+37
+00:01:30,000 --> 00:01:32,000
+And this is actually very important.
+
+38
+00:01:32,000 --> 00:01:33,000
+So whenever you have a value
+
+39
+00:01:33,000 --> 00:01:36,000
+which you think will not change, try to make it final.
+
+40
+00:01:36,000 --> 00:01:38,000
+It's a good practice to make final variables
+
+41
+00:01:38,000 --> 00:01:41,000
+is because you will not get any unexpected output.
+
+42
+00:01:41,000 --> 00:01:44,000
+Because if you think the value should be constant,
+
+43
+00:01:44,000 --> 00:01:45,000
+then why do you even change it?
+
+44
+00:01:45,000 --> 00:01:47,000
+Example, if you want to make a variable for pi.
+
+45
+00:01:47,000 --> 00:01:50,000
+We know the value of pi, right, which will not change.
+
+46
+00:01:50,000 --> 00:01:53,000
+So it's good to make that particular variable as final.
+
+47
+00:01:53,000 --> 00:01:55,000
+So it's always a good idea to make a final variable
+
+48
+00:01:55,000 --> 00:01:59,000
+because that's what a good practice is.
+
+49
+00:01:59,000 --> 00:02:01,000
+So we have talked about what is final variable.
+
+50
+00:02:01,000 --> 00:02:04,000
+So final variable simply means making constants.
+
+51
+00:02:04,000 --> 00:02:06,000
+Now let's talk about final method.
+
+52
+00:02:06,000 --> 00:02:08,000
+In fact, even before final method,
+
+53
+00:02:08,000 --> 00:02:09,000
+let's talk about final class.
+
+54
+00:02:09,000 --> 00:02:11,000
+Then final method will make much more sense.
+
+55
+00:02:11,000 --> 00:02:12,000
+So at this point, I will just remove this part.
+
+56
+00:02:12,000 --> 00:02:15,000
+So now we know what is final variable is, right?
+
+57
+00:02:15,000 --> 00:02:18,000
+So what I'll do here is I have a class here called,
+
+58
+00:02:18,000 --> 00:02:19,000
+let's say, calculator.
+
+59
+00:02:21,000 --> 00:02:23,000
+Now I'm making this class and in this,
+
+60
+00:02:23,000 --> 00:02:25,000
+or maybe let's keep it simple, let's say A.
+
+61
+00:02:25,000 --> 00:02:28,000
+So I've got this class A, right, and now,
+
+62
+00:02:28,000 --> 00:02:30,000
+in this class, I have some methods.
+
+63
+00:02:30,000 --> 00:02:33,000
+Let's say the method name is public void show.
+
+64
+00:02:33,000 --> 00:02:35,000
+And you know what, let's make it calculated,
+
+65
+00:02:35,000 --> 00:02:38,000
+just to make it much more sense.
+
+66
+00:02:38,000 --> 00:02:41,000
+And I will also say public void add.
+
+67
+00:02:41,000 --> 00:02:42,000
+This time I will not return the value,
+
+68
+00:02:42,000 --> 00:02:44,000
+I will just bring the output here itself.
+
+69
+00:02:44,000 --> 00:02:48,000
+I will say A into B.
+
+70
+00:02:49,000 --> 00:02:51,000
+And then I will just simply print A plus B.
+
+71
+00:02:51,000 --> 00:02:54,000
+I'm just adding it here itself, right?
+
+72
+00:02:54,000 --> 00:02:56,000
+And then we got the method, which is show,
+
+73
+00:02:56,000 --> 00:02:58,000
+and here we are saying public,
+
+74
+00:02:58,000 --> 00:03:02,000
+here we are saying "in calc show".
+
+75
+00:03:02,000 --> 00:03:05,000
+Okay, so let's say we have this class here, which is calc,
+
+76
+00:03:05,000 --> 00:03:07,000
+and then we have these two methods.
+
+77
+00:03:07,000 --> 00:03:08,000
+And if you want to make it work,
+
+78
+00:03:08,000 --> 00:03:10,000
+of course you have to get object of calc.
+
+79
+00:03:10,000 --> 00:03:13,000
+You will say Calc obj = new calc.
+
+80
+00:03:13,000 --> 00:03:15,000
+And with this object,
+
+81
+00:03:15,000 --> 00:03:16,000
+you can basically call both the methods.
+
+82
+00:03:16,000 --> 00:03:19,000
+You can say show, you can say add,
+
+83
+00:03:19,000 --> 00:03:20,000
+and you can pass two values.
+
+84
+00:03:20,000 --> 00:03:22,000
+4, let's say, 5.
+
+85
+00:03:22,000 --> 00:03:25,000
+Right, now with this, let me just compile this code
+
+86
+00:03:25,000 --> 00:03:28,000
+and run compile, no problem, and run.
+
+87
+00:03:28,000 --> 00:03:29,000
+You can see there's no issue.
+
+88
+00:03:29,000 --> 00:03:32,000
+It is printing in calc show and nine.
+
+89
+00:03:32,000 --> 00:03:35,000
+Now what if someone else is trying
+
+90
+00:03:35,000 --> 00:03:38,000
+to create a class called advanced calculator?
+
+91
+00:03:38,000 --> 00:03:43,000
+And maybe you, maybe they're trying to extend,
+
+92
+00:03:43,000 --> 00:03:44,000
+they're trying to inherit the features
+
+93
+00:03:44,000 --> 00:03:47,000
+from your class, which is calc.
+
+94
+00:03:47,000 --> 00:03:48,000
+And by the way, it's possible.
+
+95
+00:03:48,000 --> 00:03:50,000
+Anyone can inherit your method
+
+96
+00:03:50,000 --> 00:03:53,000
+or your classes, right, because it's available.
+
+97
+00:03:53,000 --> 00:03:56,000
+What I will do is I want to stop this.
+
+98
+00:03:56,000 --> 00:03:58,000
+I want to say, "Hey, you know, no one should be able
+
+99
+00:03:58,000 --> 00:04:00,000
+to extend my class."
+
+100
+00:04:00,000 --> 00:04:03,000
+You want to stop the inheritance. How will you do that?
+
+101
+00:04:03,000 --> 00:04:05,000
+So if I make this class as final,
+
+102
+00:04:05,000 --> 00:04:07,000
+you can see it will give you an error.
+
+103
+00:04:07,000 --> 00:04:11,000
+It says, "The type advanced calculator cannot be a subclass
+
+104
+00:04:11,000 --> 00:04:12,000
+of the final class."
+
+105
+00:04:12,000 --> 00:04:13,000
+That's right.
+
+106
+00:04:13,000 --> 00:04:16,000
+So once you make your class final,
+
+107
+00:04:16,000 --> 00:04:19,000
+you are basically stopping the inheritance.
+
+108
+00:04:19,000 --> 00:04:21,000
+So basically, when we talk about final variable,
+
+109
+00:04:21,000 --> 00:04:24,000
+it means you cannot change the value of it.
+
+110
+00:04:24,000 --> 00:04:28,000
+When you make a class final, it means no one can extend it.
+
+111
+00:04:28,000 --> 00:04:31,000
+You are stopping the inheritance. Okay, that makes sense.
+
+112
+00:04:31,000 --> 00:04:33,000
+Now what if your class is not final?
+
+113
+00:04:33,000 --> 00:04:35,000
+So of course anyone can use it
+
+114
+00:04:35,000 --> 00:04:36,000
+and maybe you don't have an issue
+
+115
+00:04:36,000 --> 00:04:39,000
+of people using your class for inheritance.
+
+116
+00:04:39,000 --> 00:04:41,000
+The problem which we have is
+
+117
+00:04:41,000 --> 00:04:45,000
+someone will create object of not your class,
+
+118
+00:04:45,000 --> 00:04:49,000
+but advanced calculator, and they will use your features.
+
+119
+00:04:49,000 --> 00:04:51,000
+And you are okay with it because, ultimately,
+
+120
+00:04:51,000 --> 00:04:53,000
+you are printing your own class name,
+
+121
+00:04:53,000 --> 00:04:55,000
+which is in Calc Show.
+
+122
+00:04:55,000 --> 00:04:58,000
+Or maybe I can say "by Navin".
+
+123
+00:04:58,000 --> 00:05:00,000
+Okay, so maybe this calculator is by Navin.
+
+124
+00:05:00,000 --> 00:05:03,000
+So if I compile this code and run, it'll print my name.
+
+125
+00:05:03,000 --> 00:05:05,000
+At least I'm getting the credit.
+
+126
+00:05:05,000 --> 00:05:07,000
+But what if someone says, "Hey, you know,
+
+127
+00:05:07,000 --> 00:05:09,000
+I will use your feature of addition
+
+128
+00:05:09,000 --> 00:05:11,000
+because there's no create mention,
+
+129
+00:05:11,000 --> 00:05:14,000
+but I will have my own create here.
+
+130
+00:05:14,000 --> 00:05:16,000
+So I will create my own show method,
+
+131
+00:05:16,000 --> 00:05:18,000
+method overriding, remember,
+
+132
+00:05:18,000 --> 00:05:22,000
+and I can simply print by John."
+
+133
+00:05:22,000 --> 00:05:23,000
+I'm not sure who John is,
+
+134
+00:05:23,000 --> 00:05:26,000
+but let's say if that person says "by John".
+
+135
+00:05:26,000 --> 00:05:27,000
+Now what will happen is,
+
+136
+00:05:27,000 --> 00:05:30,000
+when you execute the show method and add,
+
+137
+00:05:30,000 --> 00:05:32,000
+you can see add is my implementation
+
+138
+00:05:32,000 --> 00:05:36,000
+but they are just overriding show method
+
+139
+00:05:36,000 --> 00:05:38,000
+and it says "by John".
+
+140
+00:05:38,000 --> 00:05:39,000
+I don't want this.
+
+141
+00:05:39,000 --> 00:05:43,000
+I don't want anyone to override my method.
+
+142
+00:05:43,000 --> 00:05:47,000
+How do I do that? How do I stop method overriding?
+
+143
+00:05:47,000 --> 00:05:50,000
+In that case, you can make your method as final.
+
+144
+00:05:50,000 --> 00:05:52,000
+Now, when you make your method final,
+
+145
+00:05:52,000 --> 00:05:55,000
+which we talked about here, when you make your method final,
+
+146
+00:05:55,000 --> 00:05:57,000
+no one can override it.
+
+147
+00:05:57,000 --> 00:05:58,000
+You can see we've got an error,
+
+148
+00:05:58,000 --> 00:06:02,000
+cannot override the final method.
+
+149
+00:06:02,000 --> 00:06:04,000
+So that's how we can use final keyword.
+
+150
+00:06:04,000 --> 00:06:07,000
+We can use final keyword with variable to make it constant,
+
+151
+00:06:07,000 --> 00:06:09,000
+you can use final keyword with the class
+
+152
+00:06:09,000 --> 00:06:12,000
+to stop inheritance, and you can use final keyword
+
+153
+00:06:12,000 --> 00:06:15,000
+with method to stop method overriding.
+
+154
+00:06:15,000 --> 00:06:16,000
+So I hope final makes sense now.
+
diff --git a/02 - Core Java/061 Source-code.url b/02 - Core Java/061 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/061 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/062 Object Class equals toString hashcode_en.srt b/02 - Core Java/062 Object Class equals toString hashcode_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..3472408ec0af74da9832e581a3f31339ca9233a1
--- /dev/null
+++ b/02 - Core Java/062 Object Class equals toString hashcode_en.srt	
@@ -0,0 +1,1292 @@
+1
+00:00:00,000 --> 00:00:03,000
+(dramatic piano music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, let's talk about object class.
+
+3
+00:00:06,000 --> 00:00:07,000
+Remember when we talked about inheritance,
+
+4
+00:00:07,000 --> 00:00:10,000
+I also mentioned that every class in Java
+
+5
+00:00:10,000 --> 00:00:12,000
+extends the object class.
+
+6
+00:00:12,000 --> 00:00:16,000
+So in this video, let's try to understand, what is that?
+
+7
+00:00:16,000 --> 00:00:17,000
+So what I will do here is, first of all,
+
+8
+00:00:17,000 --> 00:00:19,000
+I will create a simple class, let's say class A.
+
+9
+00:00:19,000 --> 00:00:23,000
+So every class in Java extends the object class, right?
+
+10
+00:00:23,000 --> 00:00:24,000
+So even if you don't mention it is there.
+
+11
+00:00:24,000 --> 00:00:26,000
+But what is there inside this class?
+
+12
+00:00:26,000 --> 00:00:28,000
+So what I will do is, first of all I will say,
+
+13
+00:00:28,000 --> 00:00:30,000
+let me get object of A here.
+
+14
+00:00:30,000 --> 00:00:34,000
+I will say A and okay, so we got the object.
+
+15
+00:00:34,000 --> 00:00:36,000
+But then using this object,
+
+16
+00:00:36,000 --> 00:00:38,000
+you can see we can call so many methods.
+
+17
+00:00:38,000 --> 00:00:40,000
+We have not defined any method in this class,
+
+18
+00:00:40,000 --> 00:00:42,000
+but still we have the access of equals method.
+
+19
+00:00:42,000 --> 00:00:47,000
+Then we got notify, hashCode, notifyAll, toString, wait.
+
+20
+00:00:48,000 --> 00:00:49,000
+So many methods, right?
+
+21
+00:00:49,000 --> 00:00:52,000
+Now what they do, so let's understand that.
+
+22
+00:00:52,000 --> 00:00:55,000
+So what I do is, in fact instead of this,
+
+23
+00:00:55,000 --> 00:00:58,000
+I will say Laptop class just for the example.
+
+24
+00:00:58,000 --> 00:01:00,000
+And here also let me get an object of Laptop here.
+
+25
+00:01:00,000 --> 00:01:05,000
+So I will say Laptop obj = new Laptop.
+
+26
+00:01:05,000 --> 00:01:09,000
+Okay, now I will try to create some variables here.
+
+27
+00:01:09,000 --> 00:01:11,000
+So I will say private int.
+
+28
+00:01:11,000 --> 00:01:14,000
+Let's say price;.
+
+29
+00:01:14,000 --> 00:01:15,000
+And let me also get a string variable here,
+
+30
+00:01:15,000 --> 00:01:18,000
+which is private String brand.
+
+31
+00:01:18,000 --> 00:01:20,000
+Okay, so we got these two laptops.
+
+32
+00:01:21,000 --> 00:01:23,000
+I can say model as well.
+
+33
+00:01:23,000 --> 00:01:24,000
+So we got model and price, right?
+
+34
+00:01:24,000 --> 00:01:28,000
+So if you talk about MacBook or Dell XPS or Lenovo laptops
+
+35
+00:01:28,000 --> 00:01:29,000
+or it doesn't matter which laptop it is,
+
+36
+00:01:29,000 --> 00:01:31,000
+we have a model and we have a price here.
+
+37
+00:01:31,000 --> 00:01:34,000
+Now if you talk about this particular laptop here,
+
+38
+00:01:34,000 --> 00:01:35,000
+let me set the values to it.
+
+39
+00:01:35,000 --> 00:01:37,000
+And timing, you know what I will do,
+
+40
+00:01:37,000 --> 00:01:38,000
+I will just remove this private
+
+41
+00:01:38,000 --> 00:01:41,000
+so that I can access it from outside here.
+
+42
+00:01:41,000 --> 00:01:42,000
+And I can say,
+
+43
+00:01:43,000 --> 00:01:45,000
+so I will say obj.model.
+
+44
+00:01:45,000 --> 00:01:49,000
+I will set the model as let's say, Lenovo,
+
+45
+00:01:49,000 --> 00:01:50,000
+I don't know, is it a Laptop Yoga?
+
+46
+00:01:50,000 --> 00:01:51,000
+Maybe.
+
+47
+00:01:51,000 --> 00:01:56,000
+And then I will say obj.price is equal to let's $1000.
+
+48
+00:01:57,000 --> 00:01:58,000
+Okay, so I got a laptop.
+
+49
+00:01:58,000 --> 00:02:00,000
+I've got the values, right?
+
+50
+00:02:00,000 --> 00:02:02,000
+What if I try to print the object?
+
+51
+00:02:02,000 --> 00:02:03,000
+What happens behind the scene
+
+52
+00:02:03,000 --> 00:02:05,000
+when I try to print the object?
+
+53
+00:02:05,000 --> 00:02:06,000
+Of course we tried this before
+
+54
+00:02:06,000 --> 00:02:09,000
+and it was giving some weird output.
+
+55
+00:02:09,000 --> 00:02:11,000
+Let's understand what that output is.
+
+56
+00:02:11,000 --> 00:02:13,000
+Now if you try to concentrate on this output,
+
+57
+00:02:13,000 --> 00:02:16,000
+of course, this is not the values which we set,
+
+58
+00:02:16,000 --> 00:02:18,000
+but it prints laptop and it actually makes sense
+
+59
+00:02:18,000 --> 00:02:21,000
+because obj is a laptop object.
+
+60
+00:02:21,000 --> 00:02:24,000
+And then we got the at rate symbol
+
+61
+00:02:24,000 --> 00:02:26,000
+and then we got some weird numbers.
+
+62
+00:02:26,000 --> 00:02:29,000
+I'm assuming they are hexidecimal values
+
+63
+00:02:29,000 --> 00:02:32,000
+because you can see we got a, d, f.
+
+64
+00:02:32,000 --> 00:02:34,000
+They are part of hexidecimal numbers.
+
+65
+00:02:34,000 --> 00:02:35,000
+Okay, so these are hexidecimal format.
+
+66
+00:02:35,000 --> 00:02:37,000
+But what is it?
+
+67
+00:02:37,000 --> 00:02:38,000
+Let's try to understand that.
+
+68
+00:02:38,000 --> 00:02:39,000
+Now what if I say,
+
+69
+00:02:39,000 --> 00:02:42,000
+every time you try to print the object
+
+70
+00:02:42,000 --> 00:02:44,000
+it by defaults behind the scene,
+
+71
+00:02:44,000 --> 00:02:47,000
+it will call the toString method.
+
+72
+00:02:47,000 --> 00:02:48,000
+Let me repeat.
+
+73
+00:02:48,000 --> 00:02:50,000
+Every time you try to print the object,
+
+74
+00:02:50,000 --> 00:02:52,000
+it will call toString method
+
+75
+00:02:52,000 --> 00:02:54,000
+even if you don't mention, yeah.
+
+76
+00:02:54,000 --> 00:02:56,000
+And okay, by doing those changes,
+
+77
+00:02:56,000 --> 00:02:58,000
+let me just run this code once again.
+
+78
+00:02:58,000 --> 00:03:00,000
+Compile and run.
+
+79
+00:03:00,000 --> 00:03:01,000
+You can see this, it prints the same thing.
+
+80
+00:03:01,000 --> 00:03:04,000
+That means yes it is getting called
+
+81
+00:03:04,000 --> 00:03:05,000
+but what toString is doing?
+
+82
+00:03:05,000 --> 00:03:08,000
+So if I go to toString, now first of all,
+
+83
+00:03:08,000 --> 00:03:10,000
+toString is not my method.
+
+84
+00:03:10,000 --> 00:03:11,000
+If you can see in laptop class
+
+85
+00:03:11,000 --> 00:03:14,000
+we don't have any method called toString.
+
+86
+00:03:14,000 --> 00:03:16,000
+But in the object class there is.
+
+87
+00:03:16,000 --> 00:03:18,000
+You can see we got a toString method
+
+88
+00:03:18,000 --> 00:03:20,000
+which returns a string, right?
+
+89
+00:03:20,000 --> 00:03:21,000
+That's what we are printing, right?
+
+90
+00:03:21,000 --> 00:03:23,000
+It returns something.
+
+91
+00:03:23,000 --> 00:03:24,000
+What it returns?
+
+92
+00:03:24,000 --> 00:03:26,000
+It returns the class name.
+
+93
+00:03:26,000 --> 00:03:26,000
+If you can see it says getClass.
+
+94
+00:03:26,000 --> 00:03:30,000
+getClass method will give you the class name.
+
+95
+00:03:30,000 --> 00:03:31,000
+Then it calls getName.
+
+96
+00:03:31,000 --> 00:03:35,000
+So class name, okay, that is laptop.
+
+97
+00:03:35,000 --> 00:03:36,000
+Okay is working.
+
+98
+00:03:36,000 --> 00:03:39,000
+And then we got at that symbol in between.
+
+99
+00:03:39,000 --> 00:03:41,000
+Okay, that also makes sense why we got added it there
+
+100
+00:03:41,000 --> 00:03:44,000
+and then it print something in hexa string.
+
+101
+00:03:44,000 --> 00:03:47,000
+That's why we got hexa symbol values here.
+
+102
+00:03:47,000 --> 00:03:48,000
+But what exactly represents?
+
+103
+00:03:48,000 --> 00:03:51,000
+It converts the number into hexadecimal string
+
+104
+00:03:51,000 --> 00:03:54,000
+and that number is actually hashCode.
+
+105
+00:03:54,000 --> 00:03:56,000
+Now what is hashCode?
+
+106
+00:03:56,000 --> 00:03:58,000
+If you go to hashCode, again it belongs to the same class
+
+107
+00:03:58,000 --> 00:04:00,000
+and behind the scene implementation
+
+108
+00:04:00,000 --> 00:04:02,000
+of a hashCode works with the,
+
+109
+00:04:02,000 --> 00:04:03,000
+it basically generates the hash
+
+110
+00:04:03,000 --> 00:04:06,000
+based on the values you have, okay.
+
+111
+00:04:06,000 --> 00:04:08,000
+Now hash is a very simple concept
+
+112
+00:04:08,000 --> 00:04:11,000
+in terms of cryptography anywhere.
+
+113
+00:04:11,000 --> 00:04:14,000
+It tries to create a single string
+
+114
+00:04:14,000 --> 00:04:16,000
+of all the data which you have.
+
+115
+00:04:16,000 --> 00:04:19,000
+So let's say if you have a object which has five variables,
+
+116
+00:04:19,000 --> 00:04:21,000
+it will apply a hash algorithm
+
+117
+00:04:21,000 --> 00:04:25,000
+and it will generate a string, a number string,
+
+118
+00:04:25,000 --> 00:04:28,000
+which will be a fixed size, okay.
+
+119
+00:04:28,000 --> 00:04:31,000
+To know more about hashCode,
+
+120
+00:04:31,000 --> 00:04:31,000
+you can just go to YouTube
+
+121
+00:04:31,000 --> 00:04:33,000
+and search for what is hash
+
+122
+00:04:33,000 --> 00:04:35,000
+or go to Google and search for what is hash.
+
+123
+00:04:35,000 --> 00:04:38,000
+But at this point we are returning a hashCode, okay?
+
+124
+00:04:38,000 --> 00:04:40,000
+That's what we got here.
+
+125
+00:04:40,000 --> 00:04:44,000
+Okay, now the thing is we are trying to print this, right?
+
+126
+00:04:44,000 --> 00:04:44,000
+So by the default is calling toString
+
+127
+00:04:44,000 --> 00:04:46,000
+and that's why we got this output.
+
+128
+00:04:46,000 --> 00:04:49,000
+But what if when I try to print the object,
+
+129
+00:04:49,000 --> 00:04:51,000
+it will print something which I want.
+
+130
+00:04:51,000 --> 00:04:53,000
+And one thing we know
+
+131
+00:04:53,000 --> 00:04:55,000
+that if you don't have a method in your class,
+
+132
+00:04:55,000 --> 00:04:56,000
+it will call the method of a super class.
+
+133
+00:04:56,000 --> 00:05:00,000
+But what if I create that method itself?
+
+134
+00:05:00,000 --> 00:05:03,000
+So the public method which returns a string,
+
+135
+00:05:03,000 --> 00:05:04,000
+the method name is toString.
+
+136
+00:05:04,000 --> 00:05:07,000
+If I implement this method
+
+137
+00:05:07,000 --> 00:05:11,000
+and if I return something, if I return say "Hey", that's it.
+
+138
+00:05:11,000 --> 00:05:15,000
+And if I clear this and compile
+
+139
+00:05:15,000 --> 00:05:18,000
+and run, oh it says Hey, you know.
+
+140
+00:05:18,000 --> 00:05:21,000
+It's not printing the laptop class name
+
+141
+00:05:21,000 --> 00:05:23,000
+and hexidecimal values.
+
+142
+00:05:23,000 --> 00:05:26,000
+It's trying to call toString, which is this.
+
+143
+00:05:26,000 --> 00:05:28,000
+it is written, "Hey".
+
+144
+00:05:28,000 --> 00:05:30,000
+It's not going for the super class here.
+
+145
+00:05:30,000 --> 00:05:31,000
+That is awesome.
+
+146
+00:05:31,000 --> 00:05:35,000
+Now let me also try by deleting this thing, okay.
+
+147
+00:05:35,000 --> 00:05:37,000
+Let's not call toString by ourself.
+
+148
+00:05:37,000 --> 00:05:39,000
+Let's see if it is getting called automatically.
+
+149
+00:05:39,000 --> 00:05:40,000
+It is happening, right?
+
+150
+00:05:40,000 --> 00:05:42,000
+Now, whatever you wanna return, you can do that here, right?
+
+151
+00:05:42,000 --> 00:05:44,000
+What I want to return is I want to return
+
+152
+00:05:44,000 --> 00:05:48,000
+the model information with colon in between
+
+153
+00:05:48,000 --> 00:05:50,000
+and the price, so that it will print
+
+154
+00:05:50,000 --> 00:05:51,000
+that particular data.
+
+155
+00:05:51,000 --> 00:05:52,000
+Compile and run.
+
+156
+00:05:52,000 --> 00:05:56,000
+You can see it says Lenovo Yoga : $1000.
+
+157
+00:05:56,000 --> 00:05:57,000
+Okay, so that's how we can basically
+
+158
+00:05:57,000 --> 00:05:59,000
+work with the object class methods.
+
+159
+00:05:59,000 --> 00:06:02,000
+If you don't mention it will be coming automatically
+
+160
+00:06:02,000 --> 00:06:04,000
+by the object class.
+
+161
+00:06:04,000 --> 00:06:05,000
+But there's one more thing.
+
+162
+00:06:05,000 --> 00:06:07,000
+Let's say if I create one more object of laptop,
+
+163
+00:06:07,000 --> 00:06:09,000
+and this time let's say the values are same.
+
+164
+00:06:09,000 --> 00:06:12,000
+Let's say this is object one, object two.
+
+165
+00:06:12,000 --> 00:06:15,000
+This is the object one, one.
+
+166
+00:06:15,000 --> 00:06:17,000
+Okay, don't give me suggestions.
+
+167
+00:06:17,000 --> 00:06:19,000
+Yeah, this is two and two.
+
+168
+00:06:19,000 --> 00:06:22,000
+Now if you compare these two objects, are they same?
+
+169
+00:06:22,000 --> 00:06:24,000
+Yes the values are same,
+
+170
+00:06:24,000 --> 00:06:26,000
+but do we have the objects which are same?
+
+171
+00:06:26,000 --> 00:06:27,000
+Let's try.
+
+172
+00:06:27,000 --> 00:06:28,000
+How will you compare this?
+
+173
+00:06:28,000 --> 00:06:30,000
+So what I can do is I can just create
+
+174
+00:06:30,000 --> 00:06:35,000
+a boolean variable here and I can say result is equal to,
+
+175
+00:06:36,000 --> 00:06:38,000
+how do I compare obj1.obj2
+
+176
+00:06:38,000 --> 00:06:41,000
+or obj1 == obj2.
+
+177
+00:06:42,000 --> 00:06:43,000
+Let's try.
+
+178
+00:06:43,000 --> 00:06:44,000
+I mean we can use double equal to
+
+179
+00:06:44,000 --> 00:06:46,000
+between obj1 and obj2 as well.
+
+180
+00:06:46,000 --> 00:06:48,000
+Let's try to print the result
+
+181
+00:06:48,000 --> 00:06:49,000
+and let's see what happens.
+
+182
+00:06:49,000 --> 00:06:53,000
+If I compile this code and run, oh it says false.
+
+183
+00:06:53,000 --> 00:06:56,000
+Okay, maybe using double equal to is not a good idea.
+
+184
+00:06:56,000 --> 00:06:57,000
+Let's use some inbuilt methods.
+
+185
+00:06:57,000 --> 00:07:02,000
+If you can see obj1 actually has a method called equals.
+
+186
+00:07:02,000 --> 00:07:04,000
+It checks for the equals.
+
+187
+00:07:04,000 --> 00:07:05,000
+Okay, that's great.
+
+188
+00:07:05,000 --> 00:07:08,000
+It checks for the equals of obj1 and obj2.
+
+189
+00:07:08,000 --> 00:07:10,000
+Okay, let me try this.
+
+190
+00:07:10,000 --> 00:07:12,000
+I hope this will work.
+
+191
+00:07:12,000 --> 00:07:13,000
+Compile and run.
+
+192
+00:07:13,000 --> 00:07:16,000
+Oh, it is still giving you false.
+
+193
+00:07:16,000 --> 00:07:17,000
+Why?
+
+194
+00:07:17,000 --> 00:07:18,000
+The objects are same, right?
+
+195
+00:07:18,000 --> 00:07:21,000
+The thing is, if you go with the equals method here
+
+196
+00:07:21,000 --> 00:07:24,000
+you can see in our class we don't have equals
+
+197
+00:07:24,000 --> 00:07:27,000
+and the equals is actually coming from the object class.
+
+198
+00:07:27,000 --> 00:07:28,000
+It basically compares the two object
+
+199
+00:07:28,000 --> 00:07:31,000
+by their hexadecimal number.
+
+200
+00:07:31,000 --> 00:07:32,000
+We don't do that.
+
+201
+00:07:32,000 --> 00:07:35,000
+So we want to compare them based on their values.
+
+202
+00:07:35,000 --> 00:07:37,000
+So one thing we can do is we can implement
+
+203
+00:07:37,000 --> 00:07:39,000
+the equals method by ourself.
+
+204
+00:07:39,000 --> 00:07:42,000
+So we want the equals method which will
+
+205
+00:07:42,000 --> 00:07:43,000
+return a boolean value.
+
+206
+00:07:43,000 --> 00:07:45,000
+The method name is equals
+
+207
+00:07:45,000 --> 00:07:47,000
+and it will accept only one object.
+
+208
+00:07:47,000 --> 00:07:50,000
+I will say this as an object of the same type, laptop,
+
+209
+00:07:50,000 --> 00:07:52,000
+because we are comparing laptop with laptop.
+
+210
+00:07:52,000 --> 00:07:53,000
+I will say this is other.
+
+211
+00:07:53,000 --> 00:07:56,000
+And then the object which is calling this equals
+
+212
+00:07:56,000 --> 00:07:57,000
+is this object.
+
+213
+00:07:57,000 --> 00:07:59,000
+And we have passed one more object here which is other.
+
+214
+00:07:59,000 --> 00:08:02,000
+Or maybe I can say this is this and that.
+
+215
+00:08:02,000 --> 00:08:03,000
+So this is that object, this object.
+
+216
+00:08:03,000 --> 00:08:05,000
+So we are comparing two objects.
+
+217
+00:08:05,000 --> 00:08:07,000
+Now how do I compare?
+
+218
+00:08:07,000 --> 00:08:12,000
+I can check if this .model.equal...
+
+219
+00:08:12,000 --> 00:08:13,000
+So when you talk about this model,
+
+220
+00:08:13,000 --> 00:08:14,000
+it's a string, right?
+
+221
+00:08:14,000 --> 00:08:16,000
+Now string has equals implemented properly.
+
+222
+00:08:16,000 --> 00:08:19,000
+So we can use string equals to compare this string.
+
+223
+00:08:19,000 --> 00:08:20,000
+And this dot,
+
+224
+00:08:20,000 --> 00:08:23,000
+we are comparing that.model, right?
+
+225
+00:08:23,000 --> 00:08:24,000
+We are comparing two strings here.
+
+226
+00:08:24,000 --> 00:08:27,000
+And we have to also compare the price.
+
+227
+00:08:27,000 --> 00:08:31,000
+this.price == that.price.
+
+228
+00:08:31,000 --> 00:08:32,000
+Now why I'm using equal to for integer
+
+229
+00:08:32,000 --> 00:08:34,000
+because that's how it works, right?
+
+230
+00:08:34,000 --> 00:08:37,000
+And we have to also say open and close.
+
+231
+00:08:37,000 --> 00:08:41,000
+If this matches, then I will return true,
+
+232
+00:08:43,000 --> 00:08:47,000
+else, I will return false.
+
+233
+00:08:48,000 --> 00:08:49,000
+Simple, right?
+
+234
+00:08:49,000 --> 00:08:50,000
+And since we have only one statement,
+
+235
+00:08:50,000 --> 00:08:55,000
+I can actually do this, right, in one line.
+
+236
+00:08:56,000 --> 00:08:58,000
+You can see I'm just comparing the values here,
+
+237
+00:08:58,000 --> 00:09:01,000
+I'm comparing these two strings, which is model, model,
+
+238
+00:09:01,000 --> 00:09:03,000
+and price and price.
+
+239
+00:09:03,000 --> 00:09:05,000
+It will not use the equals of object class.
+
+240
+00:09:05,000 --> 00:09:07,000
+It will use the equals of my own class.
+
+241
+00:09:07,000 --> 00:09:08,000
+Let's see if that works.
+
+242
+00:09:08,000 --> 00:09:10,000
+Compile and run.
+
+243
+00:09:10,000 --> 00:09:11,000
+Oh it works.
+
+244
+00:09:11,000 --> 00:09:12,000
+Can you say that we got true?
+
+245
+00:09:12,000 --> 00:09:15,000
+Now if I change the value, let's say it becomes Yoga1
+
+246
+00:09:16,000 --> 00:09:19,000
+and if I try to compile and run
+
+247
+00:09:19,000 --> 00:09:20,000
+you can see it says false
+
+248
+00:09:20,000 --> 00:09:22,000
+because we have a different value.
+
+249
+00:09:22,000 --> 00:09:23,000
+Cool.
+
+250
+00:09:23,000 --> 00:09:24,000
+Okay, in fact, you know,
+
+251
+00:09:24,000 --> 00:09:25,000
+I can actually simplify this more.
+
+252
+00:09:25,000 --> 00:09:27,000
+Why to even mention if, else?
+
+253
+00:09:27,000 --> 00:09:30,000
+Anyway this is returning true and false, right?
+
+254
+00:09:30,000 --> 00:09:33,000
+What I can actually do is the entire stuff from here,
+
+255
+00:09:33,000 --> 00:09:35,000
+you can cut this part
+
+256
+00:09:35,000 --> 00:09:38,000
+and so return the entire string
+
+257
+00:09:38,000 --> 00:09:41,000
+because the string itself will compare, right?
+
+258
+00:09:41,000 --> 00:09:43,000
+It will return true or false.
+
+259
+00:09:43,000 --> 00:09:45,000
+I can do that in one line.
+
+260
+00:09:46,000 --> 00:09:47,000
+Yeah.
+
+261
+00:09:47,000 --> 00:09:48,000
+There's one way.
+
+262
+00:09:48,000 --> 00:09:49,000
+But there are some rules in Java
+
+263
+00:09:49,000 --> 00:09:51,000
+if you are trying to do equals.
+
+264
+00:09:51,000 --> 00:09:54,000
+When you say two objects are equal,
+
+265
+00:09:54,000 --> 00:09:56,000
+of course they should have a same value
+
+266
+00:09:56,000 --> 00:09:58,000
+and they should also have a same hashCode.
+
+267
+00:09:58,000 --> 00:09:59,000
+So what I mean by that is,
+
+268
+00:09:59,000 --> 00:10:01,000
+don't define the equals
+
+269
+00:10:01,000 --> 00:10:04,000
+and equals method by yourself.
+
+270
+00:10:04,000 --> 00:10:07,000
+You can use your ID and you can say source action
+
+271
+00:10:07,000 --> 00:10:09,000
+and you can see it gives you an option
+
+272
+00:10:09,000 --> 00:10:11,000
+of generate hashCode and equals.
+
+273
+00:10:11,000 --> 00:10:12,000
+Click on that.
+
+274
+00:10:12,000 --> 00:10:14,000
+Select all the variables which you want to compare
+
+275
+00:10:14,000 --> 00:10:16,000
+and click on okay.
+
+276
+00:10:16,000 --> 00:10:18,000
+It will generate the equals method for you.
+
+277
+00:10:18,000 --> 00:10:21,000
+And you can see it does multiple checks.
+
+278
+00:10:21,000 --> 00:10:22,000
+We have only checks for the value.
+
+279
+00:10:22,000 --> 00:10:27,000
+But what if you want to check if the object is not null?
+
+280
+00:10:27,000 --> 00:10:29,000
+Maybe you want to check for the class name as well.
+
+281
+00:10:29,000 --> 00:10:31,000
+Maybe you want to check if the model
+
+282
+00:10:31,000 --> 00:10:32,000
+is not null before comparing.
+
+283
+00:10:32,000 --> 00:10:35,000
+So it does multiple checks for you.
+
+284
+00:10:35,000 --> 00:10:36,000
+It's a good practice.
+
+285
+00:10:36,000 --> 00:10:38,000
+And that's why I say sometime you have
+
+286
+00:10:38,000 --> 00:10:40,000
+to prefer your own IDE output.
+
+287
+00:10:40,000 --> 00:10:42,000
+And it also implements hashCode.
+
+288
+00:10:42,000 --> 00:10:44,000
+You know, this is how the hash code is generated.
+
+289
+00:10:44,000 --> 00:10:46,000
+Basically it takes your data
+
+290
+00:10:46,000 --> 00:10:49,000
+and works and applies some algorithm on your data
+
+291
+00:10:49,000 --> 00:10:51,000
+to generate the result.
+
+292
+00:10:51,000 --> 00:10:52,000
+If this algorithm can change,
+
+293
+00:10:52,000 --> 00:10:54,000
+you can implement your own algorithm.
+
+294
+00:10:54,000 --> 00:10:56,000
+But of course it should have all the variables
+
+295
+00:10:56,000 --> 00:10:58,000
+which should comes into play.
+
+296
+00:10:58,000 --> 00:11:00,000
+Example let's say, I have one more string here.
+
+297
+00:11:00,000 --> 00:11:02,000
+which is serial number.
+
+298
+00:11:02,000 --> 00:11:06,000
+And I'm okay if two objects have the same model number,
+
+299
+00:11:06,000 --> 00:11:08,000
+same model, same price, but different serial number.
+
+300
+00:11:08,000 --> 00:11:09,000
+That's okay with me.
+
+301
+00:11:09,000 --> 00:11:11,000
+So maybe you can just skip this serial
+
+302
+00:11:11,000 --> 00:11:13,000
+in your equals and hashCode.
+
+303
+00:11:13,000 --> 00:11:15,000
+Okay, that's the important thing.
+
+304
+00:11:15,000 --> 00:11:16,000
+The thing you have to remember here is
+
+305
+00:11:16,000 --> 00:11:19,000
+the object class has multiple methods
+
+306
+00:11:19,000 --> 00:11:22,000
+and we have worked with toString, which is here.
+
+307
+00:11:22,000 --> 00:11:23,000
+In fact, you know,
+
+308
+00:11:23,000 --> 00:11:25,000
+we don't even have to mention toString here.
+
+309
+00:11:25,000 --> 00:11:28,000
+We can right click and we say source action
+
+310
+00:11:28,000 --> 00:11:31,000
+generate toString with both the variables, okay.
+
+311
+00:11:31,000 --> 00:11:34,000
+It will generate a toString for you,
+
+312
+00:11:34,000 --> 00:11:38,000
+which gives you a much better output than what you can type.
+
+313
+00:11:38,000 --> 00:11:42,000
+Now I know by asking the code from your IDE,
+
+314
+00:11:42,000 --> 00:11:43,000
+you get these two extra annotations here,
+
+315
+00:11:43,000 --> 00:11:45,000
+in fact three.
+
+316
+00:11:45,000 --> 00:11:46,000
+This is actually,
+
+317
+00:11:46,000 --> 00:11:48,000
+we'll discuss that once we talk about annotations.
+
+318
+00:11:48,000 --> 00:11:49,000
+At this point it is not needed.
+
+319
+00:11:49,000 --> 00:11:50,000
+It's not compulsion,
+
+320
+00:11:50,000 --> 00:11:53,000
+but it has some importance which we'll discuss later.
+
+321
+00:11:53,000 --> 00:11:55,000
+Yeah, that's how we can use object class.
+
+322
+00:11:55,000 --> 00:11:59,000
+We can work with hashCode equals toString.
+
+323
+00:11:59,000 --> 00:12:01,000
+And yeah, that's it from this video.
+
diff --git a/02 - Core Java/062 Source-code.url b/02 - Core Java/062 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/062 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/063 Source-code.url b/02 - Core Java/063 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/063 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/063 Upcasting and Downcasting_en.srt b/02 - Core Java/063 Upcasting and Downcasting_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..8c09c2e3c4c791d7487654d30be7c84e7ba6a0e6
--- /dev/null
+++ b/02 - Core Java/063 Upcasting and Downcasting_en.srt	
@@ -0,0 +1,664 @@
+1
+00:00:03,000 --> 00:00:06,000
+-: In this video we'll talk about what is downcasting
+
+2
+00:00:06,000 --> 00:00:08,000
+and upcasting.
+
+3
+00:00:08,000 --> 00:00:10,000
+Now before this we have to understand what is typecasting.
+
+4
+00:00:10,000 --> 00:00:13,000
+So let's say we have a double value.
+
+5
+00:00:13,000 --> 00:00:15,000
+So let's say double D is equal to let's say 4.5.
+
+6
+00:00:16,000 --> 00:00:19,000
+And then of course I can print this value.
+
+7
+00:00:19,000 --> 00:00:21,000
+I can say D, and we all know what will be the output,
+
+8
+00:00:21,000 --> 00:00:23,000
+it will find 4.5.
+
+9
+00:00:23,000 --> 00:00:27,000
+But what if I want to save this value somewhere?
+
+10
+00:00:27,000 --> 00:00:30,000
+Like this example, if I say int is I equal to D?
+
+11
+00:00:30,000 --> 00:00:31,000
+Can we do that?
+
+12
+00:00:31,000 --> 00:00:33,000
+Can we have the double value inside integer?
+
+13
+00:00:33,000 --> 00:00:34,000
+Of course it will not support, right?
+
+14
+00:00:34,000 --> 00:00:38,000
+Because 4.5, we cannot be stored in integer.
+
+15
+00:00:38,000 --> 00:00:40,000
+So yes, we can at least store four here, right?
+
+16
+00:00:40,000 --> 00:00:44,000
+So maybe we can remove .5, we can at least store four.
+
+17
+00:00:44,000 --> 00:00:46,000
+But how will we do that?
+
+18
+00:00:46,000 --> 00:00:47,000
+By default, Java will not allow you that
+
+19
+00:00:47,000 --> 00:00:51,000
+because Java says, "Type mismatch cannot convert
+
+20
+00:00:51,000 --> 00:00:52,000
+from double to int."
+
+21
+00:00:52,000 --> 00:00:55,000
+It's because it says, "You know, you might lose data."
+
+22
+00:00:55,000 --> 00:00:58,000
+And we can say, "Hey, that's okay for me,
+
+23
+00:00:58,000 --> 00:00:59,000
+I'm okay to lose data."
+
+24
+00:00:59,000 --> 00:01:01,000
+So what you can do is you can typecast it.
+
+25
+00:01:01,000 --> 00:01:04,000
+So you can say, "Hey, I don't care what value you send,
+
+26
+00:01:04,000 --> 00:01:07,000
+just send that in the integer format. I'm okay with it."
+
+27
+00:01:07,000 --> 00:01:09,000
+Okay, so this is typecasting.
+
+28
+00:01:09,000 --> 00:01:12,000
+You are converting the type of a value, right?
+
+29
+00:01:12,000 --> 00:01:14,000
+Now by doing this, if I try to print I,
+
+30
+00:01:14,000 --> 00:01:16,000
+let's see what happens.
+
+31
+00:01:16,000 --> 00:01:18,000
+Of course we are throwing that integer, we will lose data.
+
+32
+00:01:18,000 --> 00:01:20,000
+So we are losing .5, but that's okay.
+
+33
+00:01:20,000 --> 00:01:22,000
+We at least we got four.
+
+34
+00:01:22,000 --> 00:01:25,000
+Now this is called typecasting.
+
+35
+00:01:25,000 --> 00:01:28,000
+Now coming back to the world of OOPs,
+
+36
+00:01:28,000 --> 00:01:29,000
+can we do this in OOPs?
+
+37
+00:01:29,000 --> 00:01:32,000
+So let's try, and we have talked about in items.
+
+38
+00:01:32,000 --> 00:01:35,000
+We have talked about how can we have methods
+
+39
+00:01:35,000 --> 00:01:36,000
+in two different classes.
+
+40
+00:01:36,000 --> 00:01:37,000
+How can we override those stuff?
+
+41
+00:01:37,000 --> 00:01:39,000
+Now, just to keep it simple,
+
+42
+00:01:39,000 --> 00:01:42,000
+what I will do is I will create a class here.
+
+43
+00:01:42,000 --> 00:01:45,000
+I will name this class as, let's say A.
+
+44
+00:01:45,000 --> 00:01:47,000
+I am just trying to keep things as simple as possible.
+
+45
+00:01:47,000 --> 00:01:49,000
+We could have gone with other names as well,
+
+46
+00:01:49,000 --> 00:01:51,000
+like can't quit or something.
+
+47
+00:01:51,000 --> 00:01:52,000
+But just to keep it simple,
+
+48
+00:01:52,000 --> 00:01:53,000
+let's say we have these two classes,
+
+49
+00:01:53,000 --> 00:01:55,000
+class A and class B.
+
+50
+00:01:55,000 --> 00:01:58,000
+And class B extends A.
+
+51
+00:01:58,000 --> 00:02:01,000
+So we are basically trying to achieve inheritance here.
+
+52
+00:02:01,000 --> 00:02:03,000
+And now with this, what we can do
+
+53
+00:02:03,000 --> 00:02:05,000
+is we can create object of A.
+
+54
+00:02:05,000 --> 00:02:06,000
+Of course we can do that, right?
+
+55
+00:02:06,000 --> 00:02:09,000
+We can create object of A, and that perfectly works.
+
+56
+00:02:09,000 --> 00:02:12,000
+Now, in this two classes, I want to have some methods.
+
+57
+00:02:12,000 --> 00:02:15,000
+Let's say in A, I have a method which is show,
+
+58
+00:02:15,000 --> 00:02:17,000
+or maybe I will say show1,
+
+59
+00:02:18,000 --> 00:02:20,000
+and in B, I can have a method
+
+60
+00:02:20,000 --> 00:02:23,000
+which is public void show2, right?
+
+61
+00:02:23,000 --> 00:02:25,000
+And then I will just print something here,
+
+62
+00:02:25,000 --> 00:02:29,000
+so I can print in a show.
+
+63
+00:02:29,000 --> 00:02:31,000
+And now you know what I would say here.
+
+64
+00:02:31,000 --> 00:02:33,000
+See, we can write any complex logic for it, right?
+
+65
+00:02:33,000 --> 00:02:35,000
+But the idea here is to understand the concepts.
+
+66
+00:02:35,000 --> 00:02:38,000
+That's what you're focusing, so in B show.
+
+67
+00:02:38,000 --> 00:02:40,000
+Now what I wanna do is using this A object,
+
+68
+00:02:40,000 --> 00:02:44,000
+so if you can see we are creating this obj of type A,
+
+69
+00:02:44,000 --> 00:02:47,000
+and also the object is also of A, right?
+
+70
+00:02:47,000 --> 00:02:50,000
+And now with the help of this obj,
+
+71
+00:02:50,000 --> 00:02:51,000
+and you can see I'm not trying
+
+72
+00:02:51,000 --> 00:02:53,000
+to achieve method over writing here.
+
+73
+00:02:53,000 --> 00:02:54,000
+They are two different methods,
+
+74
+00:02:54,000 --> 00:02:56,000
+Show1, show2, two different methods,
+
+75
+00:02:56,000 --> 00:02:58,000
+and I can call show1.
+
+76
+00:02:58,000 --> 00:02:59,000
+And you can see I can only call show1.
+
+77
+00:02:59,000 --> 00:03:00,000
+I can't call show2.
+
+78
+00:03:00,000 --> 00:03:02,000
+What's the reason I can't call show2?
+
+79
+00:03:02,000 --> 00:03:03,000
+It's very simple.
+
+80
+00:03:03,000 --> 00:03:06,000
+We don't have show2 inside A,
+
+81
+00:03:06,000 --> 00:03:09,000
+and A don't even know B exists.
+
+82
+00:03:09,000 --> 00:03:09,000
+Okay, that's a fact.
+
+83
+00:03:09,000 --> 00:03:14,000
+B knows what A is, but A has no idea what B is.
+
+84
+00:03:14,000 --> 00:03:16,000
+I hope that is not the scene in real world,
+
+85
+00:03:16,000 --> 00:03:17,000
+your parents knows you.
+
+86
+00:03:17,000 --> 00:03:21,000
+So let's try this.
+
+87
+00:03:21,000 --> 00:03:22,000
+Compile and run.
+
+88
+00:03:22,000 --> 00:03:24,000
+You can see it says, "in A Show."
+
+89
+00:03:24,000 --> 00:03:27,000
+But now my question to you is,
+
+90
+00:03:27,000 --> 00:03:31,000
+can I have the reference of A and object of B?
+
+91
+00:03:31,000 --> 00:03:33,000
+And then we have seen that, it is possible.
+
+92
+00:03:33,000 --> 00:03:34,000
+I can actually create this.
+
+93
+00:03:34,000 --> 00:03:37,000
+I can have a reference of A and object of B.
+
+94
+00:03:37,000 --> 00:03:39,000
+We have done that in dynamic method dispatch.
+
+95
+00:03:39,000 --> 00:03:41,000
+We can basically do this, right?
+
+96
+00:03:41,000 --> 00:03:43,000
+Now what you're trying to do here is,
+
+97
+00:03:43,000 --> 00:03:46,000
+we have an object of class, subclass,
+
+98
+00:03:46,000 --> 00:03:49,000
+and then we are trying to assign that to a parent class.
+
+99
+00:03:49,000 --> 00:03:51,000
+Now we can actually say, "Hey, you know
+
+100
+00:03:51,000 --> 00:03:53,000
+what you can do? Please typecast it."
+
+101
+00:03:53,000 --> 00:03:55,000
+So whatever object you're sending is of child class,
+
+102
+00:03:55,000 --> 00:03:59,000
+but typecast it with A, which is a parent class.
+
+103
+00:03:59,000 --> 00:04:01,000
+The same thing we have done for the integer double, right?
+
+104
+00:04:01,000 --> 00:04:03,000
+Now, when you are doing this,
+
+105
+00:04:03,000 --> 00:04:05,000
+we are basically going up, right?
+
+106
+00:04:05,000 --> 00:04:08,000
+Which is if you try to compare this A and B,
+
+107
+00:04:08,000 --> 00:04:11,000
+A is a super class, B is a subclass.
+
+108
+00:04:11,000 --> 00:04:14,000
+So we are trying to say, refer, I mean object is of B,
+
+109
+00:04:14,000 --> 00:04:16,000
+but refer to A.
+
+110
+00:04:16,000 --> 00:04:18,000
+So we are going up, which is upcasting.
+
+111
+00:04:18,000 --> 00:04:21,000
+So this concept here is called upcasting,
+
+112
+00:04:21,000 --> 00:04:23,000
+and of course this will work.
+
+113
+00:04:23,000 --> 00:04:27,000
+There is no issue, you can still call in a show,
+
+114
+00:04:27,000 --> 00:04:30,000
+because in B as well, we got the same method.
+
+115
+00:04:30,000 --> 00:04:33,000
+Even if you have the object of B, it will still work.
+
+116
+00:04:33,000 --> 00:04:35,000
+Okay, so this is called upcasting.
+
+117
+00:04:35,000 --> 00:04:37,000
+So, even this is not compulsory,
+
+118
+00:04:37,000 --> 00:04:41,000
+it is something which happens implicitly behind the scene.
+
+119
+00:04:41,000 --> 00:04:44,000
+So you don't have even have to mention the casting part.
+
+120
+00:04:44,000 --> 00:04:45,000
+It normally works.
+
+121
+00:04:45,000 --> 00:04:47,000
+So this is upcasting.
+
+122
+00:04:47,000 --> 00:04:48,000
+Now what is downcasting?
+
+123
+00:04:49,000 --> 00:04:52,000
+So let's say I'm creating a reference of B.
+
+124
+00:04:52,000 --> 00:04:55,000
+Now why we have to go for downcasting first of all?
+
+125
+00:04:55,000 --> 00:04:58,000
+See, using this, even if the object is of B,
+
+126
+00:04:58,000 --> 00:05:01,000
+using this obj, I can't call show2.
+
+127
+00:05:01,000 --> 00:05:03,000
+If you can see the object is of B,
+
+128
+00:05:03,000 --> 00:05:05,000
+and the method show2 belongs to B,
+
+129
+00:05:05,000 --> 00:05:07,000
+but still you can't call it.
+
+130
+00:05:07,000 --> 00:05:09,000
+Reason is because the reference is of A,
+
+131
+00:05:09,000 --> 00:05:13,000
+and A has no idea what is this show2, okay?
+
+132
+00:05:13,000 --> 00:05:14,000
+So to solve that problem,
+
+133
+00:05:14,000 --> 00:05:16,000
+what we can do is we can create a new reference,
+
+134
+00:05:16,000 --> 00:05:19,000
+let's say obj1, but then I want to use the same object.
+
+135
+00:05:19,000 --> 00:05:20,000
+I don't want to get a new object.
+
+136
+00:05:20,000 --> 00:05:23,000
+Of course you can do this, but you're getting a new object.
+
+137
+00:05:23,000 --> 00:05:24,000
+Can we do this?
+
+138
+00:05:24,000 --> 00:05:27,000
+Can we say obj1 is equal to obj?
+
+139
+00:05:27,000 --> 00:05:31,000
+Now the problem is even obj is referring to B object,
+
+140
+00:05:31,000 --> 00:05:33,000
+but the problem is, it is referred to A.
+
+141
+00:05:33,000 --> 00:05:35,000
+It's the type of obj is A.
+
+142
+00:05:35,000 --> 00:05:39,000
+So it's the same problem of double and int, right? Similar.
+
+143
+00:05:39,000 --> 00:05:42,000
+So what we can do is, we can do a typecasting here.
+
+144
+00:05:42,000 --> 00:05:46,000
+We can say, "Hey, I know this is reference of A,
+
+145
+00:05:46,000 --> 00:05:47,000
+but the object is of B, right?"
+
+146
+00:05:47,000 --> 00:05:51,000
+So whenever you assign, I want the type to be of B,
+
+147
+00:05:51,000 --> 00:05:52,000
+and that's how it works.
+
+148
+00:05:52,000 --> 00:05:54,000
+This is called downcasting.
+
+149
+00:05:54,000 --> 00:05:58,000
+So this obj is the parent object or parent reference.
+
+150
+00:05:58,000 --> 00:06:01,000
+You are downcasting it to the child reference.
+
+151
+00:06:01,000 --> 00:06:03,000
+Now using this new obj1, I can call show2.
+
+152
+00:06:05,000 --> 00:06:08,000
+Okay, so this is downcasting.
+
+153
+00:06:08,000 --> 00:06:09,000
+This is downcasting.
+
+154
+00:06:09,000 --> 00:06:11,000
+This is upcasting.
+
+155
+00:06:11,000 --> 00:06:13,000
+In general, they're called typecasting, okay?
+
+156
+00:06:15,000 --> 00:06:16,000
+So you don't have to actually remember
+
+157
+00:06:16,000 --> 00:06:17,000
+these terms every time
+
+158
+00:06:17,000 --> 00:06:19,000
+upcasting, downcasting.
+
+159
+00:06:19,000 --> 00:06:22,000
+After some time you actually, you get used to this concept.
+
+160
+00:06:22,000 --> 00:06:26,000
+You will implicitly use those things anywhere you want.
+
+161
+00:06:26,000 --> 00:06:28,000
+But yes, while teaching, we have to use some words.
+
+162
+00:06:28,000 --> 00:06:30,000
+So upcasting, downcasting.
+
+163
+00:06:30,000 --> 00:06:32,000
+So yeah, that's about this concept.
+
+164
+00:06:32,000 --> 00:06:34,000
+But remember this, we can create a parent reference
+
+165
+00:06:34,000 --> 00:06:37,000
+and child object and we can also come back
+
+166
+00:06:37,000 --> 00:06:39,000
+to the child reference here.
+
diff --git a/02 - Core Java/064 Source-Code.url b/02 - Core Java/064 Source-Code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/02 - Core Java/064 Source-Code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/02 - Core Java/064 Wrapper Class_en.srt b/02 - Core Java/064 Wrapper Class_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..f4319b346b843f082f533348062f3eca2bbc0242
--- /dev/null
+++ b/02 - Core Java/064 Wrapper Class_en.srt	
@@ -0,0 +1,884 @@
+1
+00:00:00,000 --> 00:00:02,000
+-: Let's talk about wrapper classes.
+
+2
+00:00:02,000 --> 00:00:04,000
+Now we have talked about primitive variables, right?
+
+3
+00:00:04,000 --> 00:00:05,000
+Example, if you want to create,
+
+4
+00:00:05,000 --> 00:00:07,000
+if you want to store a number like five,
+
+5
+00:00:07,000 --> 00:00:09,000
+of course you will store that in an INT variable
+
+6
+00:00:09,000 --> 00:00:10,000
+or maybe short, maybe byte,
+
+7
+00:00:10,000 --> 00:00:11,000
+that's your choice.
+
+8
+00:00:11,000 --> 00:00:15,000
+If you want to work with a value which is point values,
+
+9
+00:00:15,000 --> 00:00:17,000
+let's say 6.5 or something like that,
+
+10
+00:00:17,000 --> 00:00:19,000
+you will be using double or float.
+
+11
+00:00:19,000 --> 00:00:21,000
+And then if you want to store a character,
+
+12
+00:00:21,000 --> 00:00:23,000
+you will use a char, right?
+
+13
+00:00:23,000 --> 00:00:25,000
+So Java does provide you primitive data types,
+
+14
+00:00:25,000 --> 00:00:28,000
+and that's what makes Java
+
+15
+00:00:28,000 --> 00:00:31,000
+99.99% object-oriented.
+
+16
+00:00:31,000 --> 00:00:34,000
+That's right, Java is not purely object-oriented
+
+17
+00:00:34,000 --> 00:00:36,000
+because say when you talk about a language
+
+18
+00:00:36,000 --> 00:00:37,000
+like object-oriented programming language,
+
+19
+00:00:37,000 --> 00:00:40,000
+it means that everything should be object.
+
+20
+00:00:40,000 --> 00:00:41,000
+But that's not the case with Java.
+
+21
+00:00:41,000 --> 00:00:42,000
+Java says, okay, we are still going to work
+
+22
+00:00:42,000 --> 00:00:45,000
+with something which is not extending object.
+
+23
+00:00:45,000 --> 00:00:49,000
+As we know, every class in Java extends object class,
+
+24
+00:00:49,000 --> 00:00:50,000
+but not the primitive values.
+
+25
+00:00:50,000 --> 00:00:51,000
+If I talk about INT, float,
+
+26
+00:00:51,000 --> 00:00:53,000
+they are primitive types.
+
+27
+00:00:53,000 --> 00:00:55,000
+They are not object types, right?
+
+28
+00:00:56,000 --> 00:01:00,000
+It's good because it helps Java to improve the performance
+
+29
+00:01:00,000 --> 00:01:02,000
+because it directly works with the fixed site value, right?
+
+30
+00:01:02,000 --> 00:01:06,000
+So it is not saved in a heap memory as an object,
+
+31
+00:01:06,000 --> 00:01:08,000
+which will be time consuming.
+
+32
+00:01:08,000 --> 00:01:10,000
+So what it says is, if you want to show the value,
+
+33
+00:01:10,000 --> 00:01:12,000
+you can do that directly in primitive,
+
+34
+00:01:12,000 --> 00:01:14,000
+but then there are certain features,
+
+35
+00:01:14,000 --> 00:01:15,000
+there are certain frameworks in Java,
+
+36
+00:01:15,000 --> 00:01:17,000
+which only works with objects.
+
+37
+00:01:17,000 --> 00:01:18,000
+Example, let's say in future,
+
+38
+00:01:18,000 --> 00:01:20,000
+we are gonna talk about collection framework.
+
+39
+00:01:20,000 --> 00:01:23,000
+In collection, if you want to store values.
+
+40
+00:01:23,000 --> 00:01:24,000
+So just to give you a heads up,
+
+41
+00:01:24,000 --> 00:01:28,000
+collection is basically similar to array at this point.
+
+42
+00:01:28,000 --> 00:01:30,000
+Just remember that. And we can have multiple values.
+
+43
+00:01:30,000 --> 00:01:33,000
+In array, we can have these primitive types,
+
+44
+00:01:33,000 --> 00:01:34,000
+but not in collection.
+
+45
+00:01:34,000 --> 00:01:36,000
+You need to have object type,
+
+46
+00:01:36,000 --> 00:01:38,000
+and that's why Java says, let me introduce something.
+
+47
+00:01:38,000 --> 00:01:42,000
+So in Java, we got this concept called a wrapper class.
+
+48
+00:01:42,000 --> 00:01:43,000
+Now what's a wrapper class?
+
+49
+00:01:43,000 --> 00:01:46,000
+For every primitive type,
+
+50
+00:01:46,000 --> 00:01:49,000
+we are going to have a class for it.
+
+51
+00:01:49,000 --> 00:01:51,000
+Okay? So if you want to work with INT,
+
+52
+00:01:51,000 --> 00:01:53,000
+you can work with integer, which is a class.
+
+53
+00:01:53,000 --> 00:01:56,000
+And this integer class basically extends the object class.
+
+54
+00:01:56,000 --> 00:01:59,000
+You have a char, we have character as a class,
+
+55
+00:01:59,000 --> 00:02:01,000
+we have double, we have a double as a class,
+
+56
+00:02:01,000 --> 00:02:03,000
+and this goes on, maybe it is short.
+
+57
+00:02:03,000 --> 00:02:04,000
+Then we have byte.
+
+58
+00:02:04,000 --> 00:02:08,000
+For every primitive type, we have a class for it, okay?
+
+59
+00:02:08,000 --> 00:02:12,000
+And it's quite good if you want to work with a framework,
+
+60
+00:02:12,000 --> 00:02:15,000
+which only supports objects.
+
+61
+00:02:15,000 --> 00:02:16,000
+But yes, if you want to improve the performance
+
+62
+00:02:16,000 --> 00:02:19,000
+and there's no restrictions, primitive still makes sense.
+
+63
+00:02:19,000 --> 00:02:21,000
+And that's why most of the examples
+
+64
+00:02:21,000 --> 00:02:22,000
+we have used primitive type.
+
+65
+00:02:22,000 --> 00:02:24,000
+But again, there are certain requirements
+
+66
+00:02:24,000 --> 00:02:26,000
+where you have to use classes.
+
+67
+00:02:26,000 --> 00:02:28,000
+Now how do we do that? So let's cut back here.
+
+68
+00:02:28,000 --> 00:02:29,000
+Let's say I have a INT variable
+
+69
+00:02:29,000 --> 00:02:32,000
+INT NUM is equal to seven.
+
+70
+00:02:32,000 --> 00:02:35,000
+Now how do I store this value into a class type
+
+71
+00:02:35,000 --> 00:02:36,000
+or the object type?
+
+72
+00:02:36,000 --> 00:02:39,000
+So the class we have is called integer, right?
+
+73
+00:02:39,000 --> 00:02:41,000
+So let me get a variable called NUM1.
+
+74
+00:02:41,000 --> 00:02:44,000
+So that's my reference object.
+
+75
+00:02:44,000 --> 00:02:45,000
+Now a reference variable, this is a primitive variable.
+
+76
+00:02:45,000 --> 00:02:47,000
+This is a reference variable.
+
+77
+00:02:47,000 --> 00:02:51,000
+Now since this is a class integer, we can say new integer.
+
+78
+00:02:52,000 --> 00:02:54,000
+And in this integer we can say
+
+79
+00:02:54,000 --> 00:02:55,000
+whatever value you want to store.
+
+80
+00:02:55,000 --> 00:02:57,000
+Let's say I want to store eight.
+
+81
+00:02:57,000 --> 00:02:59,000
+Now you can see there's a line on this.
+
+82
+00:02:59,000 --> 00:03:02,000
+So whenever you see a line in any of the IDE,
+
+83
+00:03:02,000 --> 00:03:05,000
+it simply means this particular syntax has been deprecated.
+
+84
+00:03:05,000 --> 00:03:07,000
+Deprecated simply means it was dead.
+
+85
+00:03:07,000 --> 00:03:09,000
+Don't use it now because in future release,
+
+86
+00:03:09,000 --> 00:03:10,000
+they might remove it,
+
+87
+00:03:10,000 --> 00:03:13,000
+or we have a better alternative for that.
+
+88
+00:03:13,000 --> 00:03:14,000
+But yeah, this is one of the syntax we can use.
+
+89
+00:03:14,000 --> 00:03:16,000
+So we have new integer,
+
+90
+00:03:16,000 --> 00:03:18,000
+and you can parse a value, which you want to store.
+
+91
+00:03:18,000 --> 00:03:21,000
+And of course we will see what is a better way
+
+92
+00:03:21,000 --> 00:03:22,000
+of doing this apart from this replicated.
+
+93
+00:03:22,000 --> 00:03:24,000
+But at this point, let's continue with that.
+
+94
+00:03:24,000 --> 00:03:26,000
+And let me print NUM1,
+
+95
+00:03:26,000 --> 00:03:27,000
+and let's see if that works
+
+96
+00:03:27,000 --> 00:03:29,000
+in the same way as we were doing.
+
+97
+00:03:29,000 --> 00:03:32,000
+Okay, you can see we got a warning, there's no error.
+
+98
+00:03:32,000 --> 00:03:35,000
+We got a warning, but let's run this code,
+
+99
+00:03:35,000 --> 00:03:36,000
+and you can see we got eight.
+
+100
+00:03:36,000 --> 00:03:39,000
+If this is not a good way of assigning a value,
+
+101
+00:03:39,000 --> 00:03:40,000
+what is a good way?
+
+102
+00:03:40,000 --> 00:03:42,000
+What we can actually do is instead of assigning like this,
+
+103
+00:03:42,000 --> 00:03:45,000
+we can directly assign a value called eight here.
+
+104
+00:03:45,000 --> 00:03:48,000
+And this works. We can see there's no deprecated warning.
+
+105
+00:03:48,000 --> 00:03:49,000
+And if I compile this code and run,
+
+106
+00:03:49,000 --> 00:03:51,000
+there's no warning as well.
+
+107
+00:03:51,000 --> 00:03:53,000
+Now how this is happening, first of all,
+
+108
+00:03:53,000 --> 00:03:54,000
+for every time we have an integer,
+
+109
+00:03:54,000 --> 00:03:56,000
+we have a class type, right?
+
+110
+00:03:56,000 --> 00:03:58,000
+Now what is happening here is example,
+
+111
+00:03:58,000 --> 00:04:01,000
+let's say if you want to store this INT NUM variable,
+
+112
+00:04:01,000 --> 00:04:03,000
+which is a primitive type in this, instead of saying eight,
+
+113
+00:04:03,000 --> 00:04:06,000
+let me just do that here, I will parse NUM.
+
+114
+00:04:06,000 --> 00:04:10,000
+Now what we are doing is we are taking a primitive value
+
+115
+00:04:10,000 --> 00:04:11,000
+and storing that in a object.
+
+116
+00:04:11,000 --> 00:04:15,000
+Now this concept is called autoboxing.
+
+117
+00:04:15,000 --> 00:04:17,000
+So this concept is called boxing, not autoboxing.
+
+118
+00:04:17,000 --> 00:04:19,000
+This concept is called boxing
+
+119
+00:04:19,000 --> 00:04:21,000
+because you are taking a primitive value
+
+120
+00:04:21,000 --> 00:04:24,000
+and storing that in a primitive object
+
+121
+00:04:24,000 --> 00:04:26,000
+or in a wrapper object, in a class object.
+
+122
+00:04:26,000 --> 00:04:29,000
+That is called a boxing.
+
+123
+00:04:29,000 --> 00:04:31,000
+Now since this is so important,
+
+124
+00:04:31,000 --> 00:04:34,000
+what they've done is you can directly assign NUM now,
+
+125
+00:04:34,000 --> 00:04:37,000
+so this boxing is happening automatically.
+
+126
+00:04:37,000 --> 00:04:40,000
+See behind the scene, the NUM is a primitive type, right?
+
+127
+00:04:40,000 --> 00:04:42,000
+This NUM1 isn't reference variable.
+
+128
+00:04:42,000 --> 00:04:43,000
+So of course it should be an object.
+
+129
+00:04:43,000 --> 00:04:47,000
+So this will be getting converted to object automatically,
+
+130
+00:04:47,000 --> 00:04:49,000
+and that's why we say that is autoboxing
+
+131
+00:04:49,000 --> 00:04:51,000
+when you convert it automatically, okay?
+
+132
+00:04:52,000 --> 00:04:54,000
+How do you assign the value to again, a primitive value?
+
+133
+00:04:54,000 --> 00:04:56,000
+Let's say we have NUM2,
+
+134
+00:04:56,000 --> 00:04:59,000
+and I want to assign the value of NUM1 to NUM2 now.
+
+135
+00:04:59,000 --> 00:05:02,000
+In this case you can say NUM1,
+
+136
+00:05:02,000 --> 00:05:05,000
+and then this number is an object type, right?
+
+137
+00:05:05,000 --> 00:05:06,000
+You have to get the value.
+
+138
+00:05:06,000 --> 00:05:08,000
+So you can say get integer,
+
+139
+00:05:08,000 --> 00:05:11,000
+and you can parse the value, which is NUM1.
+
+140
+00:05:11,000 --> 00:05:13,000
+Or you can parse, you can simply say get integer.
+
+141
+00:05:13,000 --> 00:05:16,000
+Okay, get integer giving you an -
+
+142
+00:05:16,000 --> 00:05:18,000
+Okay, so not get integer, we have to -
+
+143
+00:05:18,000 --> 00:05:20,000
+we have to use a different method.
+
+144
+00:05:20,000 --> 00:05:22,000
+So you have to say dot what's the method name?
+
+145
+00:05:22,000 --> 00:05:24,000
+Yeah, so we got INT value.
+
+146
+00:05:24,000 --> 00:05:25,000
+So the method name is INT value.
+
+147
+00:05:25,000 --> 00:05:28,000
+So from this object, which is of type integer,
+
+148
+00:05:28,000 --> 00:05:29,000
+you can say integer class,
+
+149
+00:05:29,000 --> 00:05:31,000
+which has lot of different methods.
+
+150
+00:05:31,000 --> 00:05:33,000
+If you scroll down for different features,
+
+151
+00:05:33,000 --> 00:05:35,000
+you can use different methods here.
+
+152
+00:05:35,000 --> 00:05:37,000
+But then if you want to get the integer value,
+
+153
+00:05:37,000 --> 00:05:38,000
+you can say INT value.
+
+154
+00:05:38,000 --> 00:05:41,000
+And then if you try to print NUM2, okay,
+
+155
+00:05:41,000 --> 00:05:42,000
+it'll give you the same value.
+
+156
+00:05:42,000 --> 00:05:43,000
+Compile and run.
+
+157
+00:05:43,000 --> 00:05:46,000
+And you can see we got seven, right?
+
+158
+00:05:46,000 --> 00:05:50,000
+The thing is, if you do this, you are saying unboxing
+
+159
+00:05:50,000 --> 00:05:53,000
+because you are getting a value from the object type
+
+160
+00:05:53,000 --> 00:05:55,000
+to a primitive type, right?
+
+161
+00:05:55,000 --> 00:05:57,000
+But what if you don't do it manually?
+
+162
+00:05:57,000 --> 00:05:59,000
+You directly assign NUM1 will this work,
+
+163
+00:05:59,000 --> 00:06:01,000
+and you can say there's no problem.
+
+164
+00:06:01,000 --> 00:06:03,000
+Now since this is happening automatically,
+
+165
+00:06:03,000 --> 00:06:05,000
+we call this auto-unboxing.
+
+166
+00:06:05,000 --> 00:06:07,000
+So what is autoboxing?
+
+167
+00:06:07,000 --> 00:06:09,000
+Is when you store a primitive type
+
+168
+00:06:09,000 --> 00:06:11,000
+in the object automatically.
+
+169
+00:06:11,000 --> 00:06:13,000
+And what is auto-unboxing is when you take out the value,
+
+170
+00:06:13,000 --> 00:06:17,000
+the primitive value from the object.
+
+171
+00:06:17,000 --> 00:06:20,000
+So this is auto-unboxing, and as I mentioned before,
+
+172
+00:06:20,000 --> 00:06:21,000
+we have different classes.
+
+173
+00:06:21,000 --> 00:06:22,000
+Example, we can also use double,
+
+174
+00:06:22,000 --> 00:06:24,000
+Even double is a class.
+
+175
+00:06:24,000 --> 00:06:26,000
+So you can see it's a class,
+
+176
+00:06:26,000 --> 00:06:29,000
+and we can use character as well.
+
+177
+00:06:29,000 --> 00:06:30,000
+Just write out.
+
+178
+00:06:30,000 --> 00:06:33,000
+Now apart from this autoboxing and boxing,
+
+179
+00:06:33,000 --> 00:06:35,000
+INT, integer provides you one more thing.
+
+180
+00:06:35,000 --> 00:06:39,000
+Let's say I have a string data here, which is string.
+
+181
+00:06:39,000 --> 00:06:40,000
+Let's say STR.
+
+182
+00:06:40,000 --> 00:06:42,000
+And the value in this is actually seven
+
+183
+00:06:42,000 --> 00:06:45,000
+or maybe some other value, let's say 12.
+
+184
+00:06:45,000 --> 00:06:48,000
+Now I got this 12 here, which is a number,
+
+185
+00:06:48,000 --> 00:06:50,000
+but it is stored in a string format, okay?
+
+186
+00:06:50,000 --> 00:06:53,000
+And then if I want to print this, if I want to print STR,
+
+187
+00:06:53,000 --> 00:06:55,000
+maybe I want to perform some operation on this,
+
+188
+00:06:55,000 --> 00:06:57,000
+maybe I want to double the value.
+
+189
+00:06:57,000 --> 00:07:01,000
+So can I say STR into two. This will not work, right?
+
+190
+00:07:01,000 --> 00:07:03,000
+Because STR is a string,
+
+191
+00:07:03,000 --> 00:07:05,000
+you can't perform an operation there.
+
+192
+00:07:05,000 --> 00:07:06,000
+So what you can do is
+
+193
+00:07:06,000 --> 00:07:08,000
+you can take this value into integer format.
+
+194
+00:07:08,000 --> 00:07:09,000
+You can say integer.
+
+195
+00:07:10,000 --> 00:07:12,000
+Maybe NUM3.
+
+196
+00:07:12,000 --> 00:07:14,000
+And in this NUM3, I want to store this 12.
+
+197
+00:07:14,000 --> 00:07:18,000
+How do you get a integer from a string?
+
+198
+00:07:18,000 --> 00:07:20,000
+Now for that there is a class called integer,
+
+199
+00:07:20,000 --> 00:07:22,000
+which we are using,
+
+200
+00:07:22,000 --> 00:07:24,000
+and this class has a method called parse INT.
+
+201
+00:07:24,000 --> 00:07:27,000
+Now parse INT is a method which will take the string,
+
+202
+00:07:27,000 --> 00:07:30,000
+and it'll convert that into integer
+
+203
+00:07:30,000 --> 00:07:31,000
+and I can simply say STR,
+
+204
+00:07:31,000 --> 00:07:34,000
+and it will take the value from the STR,
+
+205
+00:07:34,000 --> 00:07:36,000
+convert that into integer and store it in the NUM3,
+
+206
+00:07:36,000 --> 00:07:38,000
+and you can perform NUM3 into two.
+
+207
+00:07:38,000 --> 00:07:40,000
+Okay, so integer is great.
+
+208
+00:07:40,000 --> 00:07:41,000
+This is called a wrapper class
+
+209
+00:07:41,000 --> 00:07:44,000
+because it's a wrapper around a primitive type,
+
+210
+00:07:44,000 --> 00:07:45,000
+but it provides you multiple features.
+
+211
+00:07:45,000 --> 00:07:47,000
+One of them is parse INT.
+
+212
+00:07:47,000 --> 00:07:50,000
+Let's see if that works. Compile and run.
+
+213
+00:07:50,000 --> 00:07:51,000
+And it worked. Can you see that?
+
+214
+00:07:51,000 --> 00:07:53,000
+We've got 24 here.
+
+215
+00:07:53,000 --> 00:07:55,000
+So yeah, that's about the wrapper classes.
+
+216
+00:07:55,000 --> 00:07:57,000
+As I mentioned, we have multiple classes available.
+
+217
+00:07:57,000 --> 00:07:58,000
+Try them out.
+
+218
+00:07:58,000 --> 00:08:00,000
+And if you directly assign a primitive value
+
+219
+00:08:00,000 --> 00:08:04,000
+to the object type, it is called autoboxing.
+
+220
+00:08:04,000 --> 00:08:05,000
+And when you want to fetch the value automatically,
+
+221
+00:08:05,000 --> 00:08:07,000
+that is auto-unboxing.
+
diff --git a/02 - Core Java/065 Quiz 3.html b/02 - Core Java/065 Quiz 3.html
new file mode 100644
index 0000000000000000000000000000000000000000..12ac92943edc51bb469aae3e43f9cbf186152d70
--- /dev/null
+++ b/02 - Core Java/065 Quiz 3.html	
@@ -0,0 +1,479 @@
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8" />
+        <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+        <title>Quiz</title>
+        <style>
+            * {
+                font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell,
+                    "Open Sans", "Helvetica Neue", sans-serif;
+                margin: 0;
+                padding: 0;
+                box-sizing: border-box;
+                font-size: 16px;
+            }
+
+            main {
+                padding-top: 48px;
+            }
+
+            :root {
+                --large-device-width: 850px;
+                --primary-color: #0f172a;
+                --secondary-color: #020617;
+                --primary-text-color: #c7d1dd;
+                --secondary-text-color: #061602;
+                --success-background: hsl(159, 82%, 24%);
+                --success-foreground: hsl(164, 86%, 16%);
+                --success: hsl(160, 84%, 39%);
+                --danger: #ef4444;
+                --warning: #f59e0b;
+                --info-background: hsl(218, 81%, 8%);
+                --info-foreground: hsl(217, 91%, 85%);
+                --border-color: #d1d7dc;
+                --check-box-size: 20px;
+                /* control the size */
+                --check-box-color: var(--info-foreground);
+                /* the active color */
+            }
+
+            body {
+                position: relative;
+                background-color: #020617;
+                color: var(--primary-text-color);
+            }
+
+            #score-stats-container {
+                position: fixed;
+                z-index: 10;
+                top: 0;
+                height: 40px;
+                width: 100%;
+                background-color: var(--info-background);
+
+                padding: 0px 16px;
+                color: var(--info-foreground);
+                font-weight: 600;
+                display: flex;
+                align-items: center;
+                justify-content: space-between;
+            }
+
+            #quiz-container {
+                border-radius: 8px;
+                display: flex;
+                gap: 16px;
+                flex-direction: column;
+            }
+
+            input[type="radio"] {
+                height: var(--check-box-size);
+                aspect-ratio: 1;
+                border: calc(var(--check-box-size) / 8) solid #939393;
+                padding: calc(var(--check-box-size) / 8);
+                background: radial-gradient(farthest-side, var(--check-box-color) 94%, #0000) 50%/0 0 no-repeat
+                    content-box;
+                border-radius: 50%;
+                outline-offset: calc(var(--check-box-size) / 10);
+                -webkit-appearance: none;
+                -moz-appearance: none;
+                appearance: none;
+                cursor: pointer;
+                font-size: inherit;
+                transition: 0.3s;
+            }
+
+            input[type="radio"]:checked {
+                border-color: var(--check-box-color);
+                background-size: 100% 100%;
+            }
+
+            input[type="radio"]:disabled {
+                background: linear-gradient(#939393 0 0) 50%/100% 20% no-repeat content-box;
+                opacity: 0.5;
+                cursor: not-allowed;
+            }
+
+            label {
+                display: inline-flex;
+                align-items: center;
+                gap: 10px;
+                cursor: pointer;
+                padding: 4px 6px;
+                border-radius: 4px;
+            }
+
+            @media (max-width: 767px) {
+                input[type="radio"],
+                label {
+                    cursor: default;
+                }
+
+                #quiz-container {
+                    margin-left: 8px;
+                    margin-right: 8px;
+                }
+            }
+
+            /* PC (Desktop devices) */
+            @media (min-width: 768px) {
+                body {
+                    display: flex;
+                    justify-content: center;
+                }
+
+                main {
+                    max-width: var(--large-device-width);
+                }
+
+                #score-stats-container {
+                    max-width: var(--large-device-width);
+                }
+
+                dialog {
+                    max-width: var(--large-device-width);
+                }
+            }
+
+            @media print {
+                input[type="radio"] {
+                    background: none !important;
+                    border-color: #939393 !important;
+                }
+
+                input[type="radio"]:checked {
+                    border-color: #939393 !important;
+                }
+            }
+
+            .question-lable {
+                display: flex;
+                align-items: center;
+                gap: 8px;
+            }
+
+            button {
+                -webkit-tap-highlight-color: transparent;
+                -webkit-touch-callout: none;
+                -webkit-user-select: none;
+                user-select: none;
+                outline: none;
+                position: relative;
+                overflow: hidden;
+                cursor: pointer;
+            }
+
+            .button {
+                background-color: var(--success-background);
+                border: none;
+                color: #f4f5f7;
+                opacity: 0.8;
+                font-size: 18px;
+                flex-grow: 1;
+                padding: 8px 16px;
+                border-radius: 8px;
+            }
+
+            .button:hover {
+                opacity: 1;
+            }
+
+            .explanation-btn {
+                border: none;
+                color: var(--success);
+                background-color: transparent;
+            }
+
+            #submit-button:active::after {
+                background-color: #ef4444;
+            }
+
+            .single-question-container {
+                background-color: var(--primary-color);
+                display: flex;
+                flex-direction: column;
+                gap: 8px;
+                padding: 16px;
+                border-radius: 8px;
+            }
+
+            #modal-content {
+                padding: 16px;
+                line-height: 24px;
+            }
+
+            dialog::backdrop {
+                background: rgba(0, 0, 0, 0.5);
+            }
+
+            dialog {
+                position: fixed;
+                border: 1px solid var(--border-color);
+                background-color: var(--primary-color);
+                color: rgb(240, 241, 248);
+                padding: 16px;
+                border-radius: 8px;
+                width: 80vw;
+                max-height: 80vh;
+                overflow: auto;
+                top: 50%;
+                left: 50%;
+                -webkit-transform: translateX(-50%) translateY(-50%);
+                -moz-transform: translateX(-50%) translateY(-50%);
+                -ms-transform: translateX(-50%) translateY(-50%);
+                transform: translateX(-50%) translateY(-50%);
+            }
+
+            #close-modal-btn {
+                position: absolute;
+                top: 4px;
+                right: 4px;
+                padding: 2px 8px;
+                border-radius: 2px;
+                border: none;
+                background-color: var(--danger);
+            }
+
+            .correct-answer label {
+                border: 2px solid var(--success);
+                width: 100%;
+            }
+
+            .incorrect-answer label {
+                border: 2px solid var(--danger);
+                width: 100%;
+            }
+
+            .options-container {
+                display: flex;
+                flex-direction: column;
+                gap: 4px;
+            }
+
+            #quiz-meta-container {
+                border-radius: 8px;
+                background-color: var(--primary-color);
+                margin-bottom: 12px;
+                padding: 8px;
+            }
+
+            #quiz-title {
+                text-align: center;
+                font-size: 24px;
+                margin-bottom: 8px;
+            }
+
+            #quiz-description {
+                line-height: 1.5;
+                padding: 2px 6px;
+            }
+        </style>
+    </head>
+
+    <body onload="main()">
+        <main>
+            <section id="quiz-meta-container">
+                <h1 id="quiz-title"></h1>
+                <p id="quiz-description"></p>
+            </section>
+            <section id="score-stats-container">
+                <div id="score-card">
+                    Score: <span id="current-score">999</span> of
+                    <span id="pass-percent">999%</span>
+                </div>
+                <div>Correct: <span id="correct-answers">999</span></div>
+                <div>Incorrect: <span id="wrong-answers">999</span></div>
+            </section>
+
+            <section id="quiz-container"></section>
+
+            <dialog id="modal" class="modal-container">
+                <div id="modal-content">
+                    <p id="modal-text"></p>
+                </div>
+            </dialog>
+        </main>
+
+        <script>
+            const quizData = {"quiz_id": 6098196, "quiz_description": null, "quiz_title": "Quiz 3", "pass_percent": null, "questions": [{"_class": "assessment", "id": 70996954, "assessment_type": "multiple-choice", "prompt": {"question": "<p>Does the new keyword allocate memory for an object during runtime in Java?</p>", "relatedLectureIds": "", "feedbacks": ["", ""], "answers": ["<p>Yes</p>", "<p>No</p>"]}, "correct_response": ["a"], "section": "", "question_plain": "Does the new keyword allocate memory for an object during runtime in Java?", "related_lectures": []}, {"_class": "assessment", "id": 70996956, "assessment_type": "multiple-choice", "prompt": {"question": "<p>Does the main() method be overloaded in Java?</p>", "relatedLectureIds": "", "feedbacks": ["", ""], "answers": ["<p>Yes</p>", "<p>No</p>"]}, "correct_response": ["a"], "section": "", "question_plain": "Does the main() method be overloaded in Java?", "related_lectures": []}, {"_class": "assessment", "id": 70996958, 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"relatedLectureIds": "", "feedbacks": ["", "", "", ""], "answers": ["<p>XY01XY02</p>", "<p>XY03XY02</p>", "<p>XY04XY03</p>", "<p>XY03XY04</p>"]}, "correct_response": ["c"], "section": "", "question_plain": "What will be printed after the execution of the given code?class Main{public static void main (String [] args) {String password[] = { \"XY01\", \"XY02\", \"XY03\", \"XY04\"};String result =\" \";for(int i = password.length-1; i&gt;=2; i--) {result = result + password[i];}System.out.println(result); }}", "related_lectures": []}]};
+            let correct = new Set();
+            let incorrect = new Set();
+            let totalNumberOfQuestions = 0;
+            const quizTitle = quizData.quiz_title;
+            const quizDescription = quizData.quiz_description;
+            const questionData = quizData.questions;
+            const passPercent = quizData.pass_percent;
+            const modalTextElement = document.getElementById("modal-text");
+            const quizContainerElement = document.getElementById("quiz-container");
+
+            const dialog = document.querySelector("dialog");
+            const showButton = document.getElementById("view-explanatin");
+            const closeButton = document.getElementById("close-modal-btn");
+            const quizTitleElement = document.getElementById("quiz-title");
+            const quizDescriptionElement = document.getElementById("quiz-description");
+
+            function main() {
+                // update quiz meta data
+                document.title = quizTitle;
+                quizTitleElement.innerHTML = quizTitle;
+                quizDescriptionElement.innerHTML = quizDescription;
+
+                const passPercentElement = document.getElementById("pass-percent");
+                passPercentElement.innerHTML = passPercent + "%";
+                totalNumberOfQuestions = questionData.length;
+                // shuffle the questionData to randomize the order of the questions
+                for (let i = questionData.length - 1; i > 0; i--) {
+                    const j = Math.floor(Math.random() * (i + 1));
+                    [questionData[i], questionData[j]] = [questionData[j], questionData[i]];
+                }
+
+                let formattedQuestions = questionData.map(formatSingleQuestionData);
+                updateScore();
+                // display the formattedQuestions
+                formattedQuestions.forEach((question, idx) => {
+                    renderSingleQuestion(question, idx + 1);
+                });
+            }
+
+            /**
+             * Formats the question data from the given QuizData object.
+             *
+             * @param {Object} singleQuizData - The singleQuizData object containing prompt and correct_response.
+             * @return {Object} The formatted question object with the following properties:
+             *   - id: The ID of the question.
+             *   - question: The text of the question.
+             *   - answers: The array of answer options.
+             *   - correctAnswer: The text of the correct answer.
+             *   - explanation: The explanation of the correct answer.
+             */
+            function formatSingleQuestionData(singleQuizData = null) {
+                const { prompt, correct_response, id } = singleQuizData;
+                const questionText = prompt.question;
+                const answers = prompt.answers;
+                const correctAnswer = correct_response[0];
+                const correctAnswerText = answers[correctAnswer.toLowerCase().charCodeAt(0) - 97];
+                const questionObj = {
+                    id: id,
+                    question: questionText,
+                    answers: answers,
+                    correctAnswer: correctAnswerText,
+                    explanation: prompt?.explanation || "",
+                };
+                return questionObj;
+            }
+
+            /**
+             * Renders a single question with its options and submit button.
+             *
+             * @param {Object} singleQuestionData - The data of the question to render.
+             * @param {number} rootIndex - The index of the question in the quiz.
+             * @return {void} return nothing.
+             */
+
+            const renderSingleQuestion = (singleQuestionData = {}, rootIndex = 1) => {
+                const { id, explanation, answers, correctAnswer, question } = singleQuestionData;
+                // shuffle the answers to randomize the order of the answers
+                for (let i = answers.length - 1; i > 0; i--) {
+                    const j = Math.floor(Math.random() * (i + 1));
+                    [answers[i], answers[j]] = [answers[j], answers[i]];
+                }
+                const optionsHTML = answers
+                    .map((option, index) => {
+                        const optionId = `${id}_${index}`;
+
+                        return `
+        <div class="question-lable">
+          <input type="radio" id="${optionId}" name="${"answer"}" value="${option}" />
+          <label for="${optionId}">${option}</label>
+        </div>
+      `;
+                    })
+
+                    .join("");
+
+                const container = document.createElement("div");
+                container.innerHTML = `
+        <form data-correct-answer="${correctAnswer}" data-question-id="${id}" class="single-question-container" onsubmit="submitButtonListener(event)">
+          <div style="display: flex;justify-content: space-between;">
+            <p style="font-weight: 600">Question ${rootIndex}:</p>
+            <button type="button" onclick="renderExplanation(event)" id="${`explanation-${id}`}" data-explanation="${explanation}" class="explanation-btn">View Explanation</button>
+          </div>
+          <p style="margin-bottom: 8px;line-height: 1.5">${question}</p>
+          <div class="options-container">
+            ${optionsHTML}
+          </div>
+          <div style="display: flex; gap: 8px;">
+            <button type="submit" id="submit-button" class="button">Submit</button>
+          </div>
+        </form>
+      `;
+                quizContainerElement.appendChild(container);
+            };
+
+            /**
+             * Updates the score on the page based on the number of correct and incorrect answers.
+             *
+             * @return {void} This function does not return a value.
+             */
+            function updateScore() {
+                const currentParcentageElement = document.getElementById("current-score");
+                const correctAnswerElement = document.getElementById("correct-answers");
+                const wrongAnswerElement = document.getElementById("wrong-answers");
+                correctAnswerElement.innerHTML = correct.size;
+                wrongAnswerElement.innerHTML = incorrect.size;
+                const score = Number((correct.size / totalNumberOfQuestions) * 100).toFixed(2);
+                currentParcentageElement.innerHTML = score;
+            }
+
+            /**
+             * Handles the event when the submit button is clicked.
+             *
+             * @param {Event} e - The event object.
+             * @return {void} This function does not return anything.
+             */
+            const submitButtonListener = (e) => {
+                e.preventDefault();
+                const formData = new FormData(e.target);
+                const form = e.target;
+                const selectedOption = e.target.querySelector('input[type="radio"]:checked');
+                if (!selectedOption) {
+                    alert("Please select an answer!");
+                    return;
+                }
+
+                let isCorrect = false;
+                const { answer: userAnswer } = Object.fromEntries(formData.entries());
+                const correctAnswer = e.target.dataset.correctAnswer;
+                const questionId = e.target.dataset.questionId;
+                if (userAnswer == correctAnswer) {
+                    correct.add(questionId);
+                    incorrect.delete(questionId);
+                    isCorrect = true;
+                } else {
+                    incorrect.add(e.target.dataset.questionId);
+                    correct.delete(questionId);
+                }
+                updateScore();
+
+                const resultClass = isCorrect ? "correct-answer" : "incorrect-answer";
+
+                form.querySelectorAll(".question-lable").forEach((label) => {
+                    label.classList.remove("correct-answer", "incorrect-answer");
+                });
+                selectedOption.closest(".question-lable").classList.add(resultClass);
+            };
+
+            function renderExplanation(ev) {
+                modalTextElement.innerHTML = ev.target.dataset?.explanation || "no explanation found";
+                dialog.showModal();
+                dialog.addEventListener("click", (event) => {
+                    if (event.target === dialog) {
+                        dialog.close();
+                    }
+                });
+            }
+        </script>
+    </body>
+</html>
diff --git a/02 - Core Java/external-links.txt b/02 - Core Java/external-links.txt
new file mode 100644
index 0000000000000000000000000000000000000000..68294d4141c2eea5f9f5bc337056e8987efc1b2c
--- /dev/null
+++ b/02 - Core Java/external-links.txt	
@@ -0,0 +1,183 @@
+
+001 Source-Code
+https://github.com/navinreddy20/Javacode.git
+
+001 Core-Java-Source
+https://go.telusko.com/javaCodeGit
+
+002 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+004 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+006 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+007 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+008 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+009 Source-Code
+https://github.com/navinreddy20/Javacode.git
+
+010 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+012 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+013 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+014 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+015 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+016 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+017 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+018 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+019 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+020 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+021 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+022 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+023 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+025 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+026 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+027 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+028 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+029 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+030 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+031 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+032 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+033 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+034 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+035 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+036 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+037 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+038 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+039 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+040 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+041 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+042 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+043 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+044 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+045 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+046 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+047 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+048 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+049 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+050 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+051 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+052 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+053 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+054 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+055 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+056 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+057 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+058 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+059 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+060 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+061 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+062 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+063 Source-code
+https://github.com/navinreddy20/Javacode.git
+
+064 Source-Code
+https://github.com/navinreddy20/Javacode.git
diff --git a/03 - Advance Java/001 Project 1- Introduction_en.srt b/03 - Advance Java/001 Project 1- Introduction_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..f05057fbcef5e596ba36f6a50ae84ea7a02b3c2c
--- /dev/null
+++ b/03 - Advance Java/001 Project 1- Introduction_en.srt	
@@ -0,0 +1,336 @@
+1
+00:00:00,000 --> 00:00:02,000
+(soft bright music)
+
+2
+00:00:02,000 --> 00:00:03,000
+-: When you learn something,
+
+3
+00:00:03,000 --> 00:00:07,000
+it's also important to implement that in a project.
+
+4
+00:00:07,000 --> 00:00:09,000
+And we don't have to wait till the end of the course
+
+5
+00:00:09,000 --> 00:00:11,000
+to work on a project, right?
+
+6
+00:00:11,000 --> 00:00:14,000
+And that's where in between we are building a project,
+
+7
+00:00:14,000 --> 00:00:16,000
+and also we are going to continue this project
+
+8
+00:00:16,000 --> 00:00:19,000
+as the module pass on.
+
+9
+00:00:19,000 --> 00:00:21,000
+Now the idea of this project is very simple.
+
+10
+00:00:21,000 --> 00:00:24,000
+What we want to build is a quiz application
+
+11
+00:00:24,000 --> 00:00:26,000
+with whatever we have learned till now.
+
+12
+00:00:26,000 --> 00:00:28,000
+Now when I say quiz application, what it means?
+
+13
+00:00:28,000 --> 00:00:30,000
+Of course we all play quiz somewhere, right?
+
+14
+00:00:30,000 --> 00:00:32,000
+Maybe you have watched a quiz show,
+
+15
+00:00:32,000 --> 00:00:35,000
+or a quiz competition, on television,
+
+16
+00:00:35,000 --> 00:00:36,000
+or it doesn't matter where.
+
+17
+00:00:36,000 --> 00:00:39,000
+But the thing is, we all know what quiz is.
+
+18
+00:00:39,000 --> 00:00:40,000
+Basically you get a set of questions,
+
+19
+00:00:40,000 --> 00:00:44,000
+and then as a player, you give the answers.
+
+20
+00:00:44,000 --> 00:00:47,000
+And if you are right, you get a score.
+
+21
+00:00:47,000 --> 00:00:48,000
+So let's say you get five questions,
+
+22
+00:00:48,000 --> 00:00:52,000
+and for every right answer, you get one point, okay?
+
+23
+00:00:52,000 --> 00:00:55,000
+And then at the end, you get your total scores.
+
+24
+00:00:55,000 --> 00:00:56,000
+That's what we want to build here.
+
+25
+00:00:56,000 --> 00:01:00,000
+Now for this, of course, I have a lot of requirements
+
+26
+00:01:00,000 --> 00:01:01,000
+coming to this particular project.
+
+27
+00:01:01,000 --> 00:01:04,000
+Maybe I want to give real-time score,
+
+28
+00:01:04,000 --> 00:01:06,000
+or maybe I can give this score at the end.
+
+29
+00:01:06,000 --> 00:01:08,000
+Maybe I want to set the timer as well.
+
+30
+00:01:08,000 --> 00:01:11,000
+So as a user, if you want to play this game,
+
+31
+00:01:11,000 --> 00:01:14,000
+you have to answer each question in 10 to 15 seconds.
+
+32
+00:01:14,000 --> 00:01:16,000
+We can do that as well.
+
+33
+00:01:16,000 --> 00:01:17,000
+But again, we'll go step by step.
+
+34
+00:01:17,000 --> 00:01:18,000
+Initially, we'll keep it very simple,
+
+35
+00:01:18,000 --> 00:01:19,000
+and then we'll move forward.
+
+36
+00:01:19,000 --> 00:01:21,000
+So the first thing is we have to understand
+
+37
+00:01:21,000 --> 00:01:22,000
+the project scenario here.
+
+38
+00:01:22,000 --> 00:01:24,000
+So what are the roles we need?
+
+39
+00:01:24,000 --> 00:01:26,000
+Basically, I need two roles here.
+
+40
+00:01:26,000 --> 00:01:29,000
+We need an admin, and we need a user.
+
+41
+00:01:29,000 --> 00:01:31,000
+Now why do we need an admin here?
+
+42
+00:01:31,000 --> 00:01:34,000
+Maybe you can say, instead of admin, we can say trainer.
+
+43
+00:01:34,000 --> 00:01:37,000
+As example, if I'm a trainer and if I'm teaching a class,
+
+44
+00:01:37,000 --> 00:01:40,000
+basically I want to create those questions, right?
+
+45
+00:01:40,000 --> 00:01:42,000
+So that when I go tomorrow to the classroom,
+
+46
+00:01:42,000 --> 00:01:44,000
+I can give them the quiz.
+
+47
+00:01:44,000 --> 00:01:47,000
+Now here, as a trainer, it is my responsibility
+
+48
+00:01:47,000 --> 00:01:48,000
+to create those questions.
+
+49
+00:01:48,000 --> 00:01:51,000
+So in one quiz, let's say we have five questions.
+
+50
+00:01:51,000 --> 00:01:53,000
+And then we have the other role, which is a player,
+
+51
+00:01:53,000 --> 00:01:55,000
+where a player will play the game.
+
+52
+00:01:55,000 --> 00:01:57,000
+Basically, they can say, okay, I want to play the quiz,
+
+53
+00:01:57,000 --> 00:01:58,000
+they will get five questions,
+
+54
+00:01:58,000 --> 00:02:01,000
+and they will choose the answers.
+
+55
+00:02:01,000 --> 00:02:03,000
+Now at this point, we don't have any DUIs,
+
+56
+00:02:03,000 --> 00:02:05,000
+of course, we'll not be creating that.
+
+57
+00:02:05,000 --> 00:02:06,000
+We'll work this with a console level.
+
+58
+00:02:06,000 --> 00:02:08,000
+So what are the things we need?
+
+59
+00:02:08,000 --> 00:02:10,000
+Basically, when a player start the game,
+
+60
+00:02:10,000 --> 00:02:12,000
+or anyone starts the game,
+
+61
+00:02:12,000 --> 00:02:14,000
+they will get an option of choosing who they are.
+
+62
+00:02:14,000 --> 00:02:16,000
+Are they a student or a trainer?
+
+63
+00:02:18,000 --> 00:02:20,000
+We'll not be starting with that complex initially,
+
+64
+00:02:20,000 --> 00:02:23,000
+we'll do it very easily, but we need this two.
+
+65
+00:02:23,000 --> 00:02:26,000
+Plus, when a user is playing it,
+
+66
+00:02:26,000 --> 00:02:28,000
+it should show the questions one by one,
+
+67
+00:02:28,000 --> 00:02:30,000
+and every time it'll ask the user,
+
+68
+00:02:30,000 --> 00:02:33,000
+hey, this is a question, what's your answer?
+
+69
+00:02:33,000 --> 00:02:35,000
+And a user can choose an option, right?
+
+70
+00:02:35,000 --> 00:02:36,000
+A or B or C,
+
+71
+00:02:36,000 --> 00:02:40,000
+or maybe a user can choose the exact name of the option.
+
+72
+00:02:40,000 --> 00:02:42,000
+So that's something we want to build.
+
+73
+00:02:42,000 --> 00:02:43,000
+Now to understand this, what we're going to do is,
+
+74
+00:02:43,000 --> 00:02:46,000
+of course, once we start going we'll get everything.
+
+75
+00:02:46,000 --> 00:02:47,000
+So what are the things we need?
+
+76
+00:02:47,000 --> 00:02:49,000
+Basically we need a editor.
+
+77
+00:02:49,000 --> 00:02:51,000
+We will continue to use VS Code.
+
+78
+00:02:51,000 --> 00:02:54,000
+Of course, you can use any IDE which you love,
+
+79
+00:02:54,000 --> 00:02:56,000
+IntelliJ IDEA, Eclipse, or we have multiple things,
+
+80
+00:02:56,000 --> 00:02:58,000
+but VS Code works.
+
+81
+00:02:58,000 --> 00:03:01,000
+And I'm creating a project here, empty project.
+
+82
+00:03:01,000 --> 00:03:03,000
+But what are the files we need?
+
+83
+00:03:03,000 --> 00:03:04,000
+And how do we get started?
+
+84
+00:03:04,000 --> 00:03:07,000
+And that we'll see in the next video.
+
diff --git a/03 - Advance Java/002 Project 1- QuestionService and Question class_en.srt b/03 - Advance Java/002 Project 1- QuestionService and Question class_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..b036e19e27f13f44e552cda1bbd59f8986eae96c
--- /dev/null
+++ b/03 - Advance Java/002 Project 1- QuestionService and Question class_en.srt	
@@ -0,0 +1,640 @@
+1
+00:00:00,000 --> 00:00:02,000
+(bright music)
+
+2
+00:00:02,000 --> 00:00:03,000
+-: So let's get started.
+
+3
+00:00:03,000 --> 00:00:06,000
+So what we need here is a main file, right?
+
+4
+00:00:06,000 --> 00:00:09,000
+Of course we don't have any file in this project yet.
+
+5
+00:00:09,000 --> 00:00:11,000
+Of course, you can create a basic project
+
+6
+00:00:11,000 --> 00:00:12,000
+where you have different folders,
+
+7
+00:00:12,000 --> 00:00:13,000
+but just to keep it simple,
+
+8
+00:00:13,000 --> 00:00:15,000
+what I will do is I will create a new file here
+
+9
+00:00:15,000 --> 00:00:18,000
+and I will name this file as maybe main,
+
+10
+00:00:18,000 --> 00:00:22,000
+because in this I'm going to have my main code
+
+11
+00:00:22,000 --> 00:00:25,000
+so I can simply say main, and it'll give me a main function,
+
+12
+00:00:25,000 --> 00:00:28,000
+but also this need to be a part of a class.
+
+13
+00:00:28,000 --> 00:00:31,000
+So I will say class main. So we got to our main method here.
+
+14
+00:00:31,000 --> 00:00:34,000
+Now, what I do from here is just to test.
+
+15
+00:00:34,000 --> 00:00:36,000
+If things are working out, I can simply say so
+
+16
+00:00:36,000 --> 00:00:40,000
+and hello just to see if this, how this is working.
+
+17
+00:00:40,000 --> 00:00:42,000
+Let's run this.
+
+18
+00:00:42,000 --> 00:00:44,000
+And also, I want to make sure
+
+19
+00:00:44,000 --> 00:00:48,000
+that I have my things ready here.
+
+20
+00:00:48,000 --> 00:00:50,000
+The thing is, my JDK gives a lot of things,
+
+21
+00:00:50,000 --> 00:00:51,000
+but the output is hello.
+
+22
+00:00:51,000 --> 00:00:54,000
+So that's what we wanted. So we got hello.
+
+23
+00:00:54,000 --> 00:00:55,000
+And that looks cool.
+
+24
+00:00:55,000 --> 00:00:56,000
+So this working out, okay,
+
+25
+00:00:56,000 --> 00:00:58,000
+but then I don't want to do any
+
+26
+00:00:58,000 --> 00:01:00,000
+of this stuff in this particular main.
+
+27
+00:01:00,000 --> 00:01:03,000
+So normally in your main, most of the things will be empty.
+
+28
+00:01:03,000 --> 00:01:05,000
+So if you wanna do something, let's create another class.
+
+29
+00:01:05,000 --> 00:01:06,000
+So what we want to do here is we want
+
+30
+00:01:06,000 --> 00:01:08,000
+to work with quiz, right?
+
+31
+00:01:08,000 --> 00:01:10,000
+And this quiz will have questions.
+
+32
+00:01:10,000 --> 00:01:11,000
+If you think about quiz,
+
+33
+00:01:11,000 --> 00:01:14,000
+the most important thing is the questions.
+
+34
+00:01:14,000 --> 00:01:16,000
+So what I will do is I will create another file here
+
+35
+00:01:16,000 --> 00:01:19,000
+where I will do all the work with the questions.
+
+36
+00:01:19,000 --> 00:01:22,000
+So creating questions, displaying the questions to the user,
+
+37
+00:01:22,000 --> 00:01:24,000
+or maybe playing a game.
+
+38
+00:01:24,000 --> 00:01:28,000
+So I will put that to the QuestionService.java.
+
+39
+00:01:28,000 --> 00:01:30,000
+Of course, there's no need to have service word,
+
+40
+00:01:30,000 --> 00:01:32,000
+but that's, that perfectly works.
+
+41
+00:01:32,000 --> 00:01:33,000
+So let's have question service.
+
+42
+00:01:33,000 --> 00:01:35,000
+It should also explain what we are doing, right?
+
+43
+00:01:35,000 --> 00:01:36,000
+So question, service.
+
+44
+00:01:36,000 --> 00:01:40,000
+And in this, let's do our actual work.
+
+45
+00:01:40,000 --> 00:01:42,000
+So what I'm going to do is,
+
+46
+00:01:42,000 --> 00:01:44,000
+the first step would be if you say you have questions,
+
+47
+00:01:44,000 --> 00:01:46,000
+how will you represent question?
+
+48
+00:01:46,000 --> 00:01:49,000
+Because every question will have certain things, right?
+
+49
+00:01:49,000 --> 00:01:50,000
+It'll have a question ID,
+
+50
+00:01:50,000 --> 00:01:52,000
+it'll have a question, actual question.
+
+51
+00:01:52,000 --> 00:01:54,000
+It'll have four options.
+
+52
+00:01:54,000 --> 00:01:58,000
+And then out of four, we'll be having one correct answer.
+
+53
+00:01:58,000 --> 00:01:59,000
+So how do you represent that?
+
+54
+00:01:59,000 --> 00:02:02,000
+So one thing I can do, which is very common,
+
+55
+00:02:02,000 --> 00:02:06,000
+maybe I can have int which represents an ID.
+
+56
+00:02:06,000 --> 00:02:08,000
+I can have a string,
+
+57
+00:02:08,000 --> 00:02:11,000
+which represents a question, the actual question.
+
+58
+00:02:11,000 --> 00:02:13,000
+Maybe instead of saying question, yeah, let's go, go
+
+59
+00:02:13,000 --> 00:02:17,000
+for question, and then we will have options like string,
+
+60
+00:02:17,000 --> 00:02:20,000
+OPT1, and then so on, right?
+
+61
+00:02:20,000 --> 00:02:23,000
+But what if you want to show five questions?
+
+62
+00:02:23,000 --> 00:02:24,000
+So don't you think we can write?
+
+63
+00:02:24,000 --> 00:02:27,000
+Of course, we can write ID one.
+
+64
+00:02:27,000 --> 00:02:30,000
+And then one more variable ID two. Same for question.
+
+65
+00:02:30,000 --> 00:02:33,000
+So instead of doing that, we have learned one concept,
+
+66
+00:02:33,000 --> 00:02:34,000
+which is using an array.
+
+67
+00:02:34,000 --> 00:02:37,000
+Okay? So instead of having five IDs, we can have one array.
+
+68
+00:02:37,000 --> 00:02:38,000
+How do we do that?
+
+69
+00:02:38,000 --> 00:02:42,000
+So, what we can do is we can create a array of ID,
+
+70
+00:02:42,000 --> 00:02:44,000
+we can create array of questions,
+
+71
+00:02:44,000 --> 00:02:46,000
+we can create ID array of options.
+
+72
+00:02:46,000 --> 00:02:51,000
+But again, the problem is why to have this thing separately.
+
+73
+00:02:51,000 --> 00:02:52,000
+In the concept of, OOPs
+
+74
+00:02:52,000 --> 00:02:54,000
+we have also understood there's something
+
+75
+00:02:54,000 --> 00:02:55,000
+called object, right?
+
+76
+00:02:55,000 --> 00:02:57,000
+Where you can, you can have a class,
+
+77
+00:02:57,000 --> 00:02:59,000
+and in class we can have multiple variables.
+
+78
+00:02:59,000 --> 00:03:01,000
+And when you create one object of it,
+
+79
+00:03:01,000 --> 00:03:04,000
+that represents one entity, one object, right?
+
+80
+00:03:04,000 --> 00:03:09,000
+So instead of having a array of ID question OPT one,
+
+81
+00:03:09,000 --> 00:03:12,000
+what if you can create one question class,
+
+82
+00:03:12,000 --> 00:03:14,000
+which will hold all the values
+
+83
+00:03:14,000 --> 00:03:16,000
+and then create a array of the questions?
+
+84
+00:03:16,000 --> 00:03:19,000
+What I'm saying is let's remove all these things.
+
+85
+00:03:19,000 --> 00:03:21,000
+Let's create a separate class,
+
+86
+00:03:21,000 --> 00:03:23,000
+which will represent a question basically.
+
+87
+00:03:23,000 --> 00:03:25,000
+So this is a question class.
+
+88
+00:03:25,000 --> 00:03:28,000
+And in this question class, I can have an ID,
+
+89
+00:03:28,000 --> 00:03:33,000
+I can have the string question, I can have string, OPT1,
+
+90
+00:03:33,000 --> 00:03:35,000
+and the list goes on.
+
+91
+00:03:35,000 --> 00:03:37,000
+We can keep it string or integer before the options.
+
+92
+00:03:37,000 --> 00:03:39,000
+But then in most of the questions,
+
+93
+00:03:39,000 --> 00:03:41,000
+you'll be having answers which are,
+
+94
+00:03:41,000 --> 00:03:42,000
+or the options which are strings.
+
+95
+00:03:42,000 --> 00:03:43,000
+So let's go with string.
+
+96
+00:03:43,000 --> 00:03:44,000
+And even if you have numbers,
+
+97
+00:03:44,000 --> 00:03:47,000
+you can represent that in string as well.
+
+98
+00:03:47,000 --> 00:03:49,000
+You just have to put double codes. And there's OPT4.
+
+99
+00:03:49,000 --> 00:03:51,000
+So these are the four options you will have.
+
+100
+00:03:51,000 --> 00:03:54,000
+And also we are going to have the right answer.
+
+101
+00:03:54,000 --> 00:03:56,000
+So I can say answer. Okay?
+
+102
+00:03:56,000 --> 00:03:58,000
+Now one more thing you can do.
+
+103
+00:03:58,000 --> 00:03:59,000
+Instead of creating four options like this,
+
+104
+00:03:59,000 --> 00:04:04,000
+you can simply create one string array by saying options.
+
+105
+00:04:04,000 --> 00:04:06,000
+And then you can have four values there.
+
+106
+00:04:06,000 --> 00:04:08,000
+Again, that's your choice, but this looks much simpler
+
+107
+00:04:08,000 --> 00:04:11,000
+to work with and we got answer as well.
+
+108
+00:04:11,000 --> 00:04:13,000
+So this is what you are doing.
+
+109
+00:04:13,000 --> 00:04:14,000
+The only thing is you have to make sure
+
+110
+00:04:14,000 --> 00:04:16,000
+that all the variables are private.
+
+111
+00:04:16,000 --> 00:04:18,000
+In the concept of encapsulation,
+
+112
+00:04:18,000 --> 00:04:19,000
+we have seen this, right?
+
+113
+00:04:19,000 --> 00:04:22,000
+So variables and methods works together
+
+114
+00:04:22,000 --> 00:04:25,000
+and you have to make sure that your variables are private.
+
+115
+00:04:25,000 --> 00:04:27,000
+So that's done. All the variables are private.
+
+116
+00:04:27,000 --> 00:04:29,000
+But then how will you access it?
+
+117
+00:04:29,000 --> 00:04:31,000
+Let's go back to encapsulation.
+
+118
+00:04:31,000 --> 00:04:33,000
+If you want to access this variable,
+
+119
+00:04:33,000 --> 00:04:35,000
+you need getters and setters, right?
+
+120
+00:04:35,000 --> 00:04:37,000
+So getters which will get data,
+
+121
+00:04:37,000 --> 00:04:39,000
+setters which will set the data.
+
+122
+00:04:39,000 --> 00:04:41,000
+So I can simply right click here
+
+123
+00:04:41,000 --> 00:04:45,000
+and I can say, source action, generate getters
+
+124
+00:04:45,000 --> 00:04:48,000
+and setters, okay, for how many variables you need
+
+125
+00:04:48,000 --> 00:04:49,000
+for all the variables, select that.
+
+126
+00:04:49,000 --> 00:04:53,000
+Click on, okay, and you can see we got all the
+
+127
+00:04:53,000 --> 00:04:54,000
+getters and setters.
+
+128
+00:04:54,000 --> 00:04:56,000
+I know it's huge, but we are not going
+
+129
+00:04:56,000 --> 00:04:58,000
+to open this file one again, right?
+
+130
+00:04:58,000 --> 00:04:59,000
+It's done and dusted.
+
+131
+00:04:59,000 --> 00:05:02,000
+So one more thing, we also need a constructor. Okay?
+
+132
+00:05:02,000 --> 00:05:03,000
+Why do we need a constructor?
+
+133
+00:05:03,000 --> 00:05:05,000
+What if you want to create a question
+
+134
+00:05:05,000 --> 00:05:07,000
+and while creating a question, maybe I want
+
+135
+00:05:07,000 --> 00:05:08,000
+to pass all the values,
+
+136
+00:05:08,000 --> 00:05:09,000
+or maybe we, let's do that later so
+
+137
+00:05:09,000 --> 00:05:11,000
+that it'll make much more sense.
+
+138
+00:05:11,000 --> 00:05:12,000
+So let's have, getters and setters that's it,
+
+139
+00:05:12,000 --> 00:05:14,000
+nothing much here.
+
+140
+00:05:14,000 --> 00:05:16,000
+Go back to your question service.
+
+141
+00:05:16,000 --> 00:05:19,000
+Now what I was saying is instead of creating the array
+
+142
+00:05:19,000 --> 00:05:22,000
+of individual values, now all the variables are there
+
+143
+00:05:22,000 --> 00:05:24,000
+inside the question class.
+
+144
+00:05:24,000 --> 00:05:29,000
+So what I can do is I can create the question array, okay?
+
+145
+00:05:29,000 --> 00:05:32,000
+So I will name this as questions equal to new
+
+146
+00:05:32,000 --> 00:05:35,000
+questions, right?
+
+147
+00:05:35,000 --> 00:05:37,000
+And I can specify how many questions I need.
+
+148
+00:05:37,000 --> 00:05:39,000
+So I need only five question at this point.
+
+149
+00:05:39,000 --> 00:05:42,000
+So we got a array of questions,
+
+150
+00:05:42,000 --> 00:05:43,000
+nothing fancy right?
+
+151
+00:05:43,000 --> 00:05:46,000
+Now at this point we have done
+
+152
+00:05:46,000 --> 00:05:49,000
+with our question class, we have done
+
+153
+00:05:49,000 --> 00:05:50,000
+with the question service.
+
+154
+00:05:50,000 --> 00:05:52,000
+But how will you add the question?
+
+155
+00:05:53,000 --> 00:05:55,000
+To start with, we'll have our own question hardcoded,
+
+156
+00:05:55,000 --> 00:05:57,000
+and then we'll see how do we get the
+
+157
+00:05:57,000 --> 00:05:58,000
+question from the user as well.
+
+158
+00:05:58,000 --> 00:06:01,000
+But at this point, we got our questions hardcoded,
+
+159
+00:06:01,000 --> 00:06:03,000
+but we have not done that yet.
+
+160
+00:06:03,000 --> 00:06:06,000
+So let's try to do that in the next video.
+
diff --git a/03 - Advance Java/003 Project 1- Hard Coded Questions and Display them_en.srt b/03 - Advance Java/003 Project 1- Hard Coded Questions and Display them_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..95ae9ece11eb1451dfd614807911c0fb8cb77e4b
--- /dev/null
+++ b/03 - Advance Java/003 Project 1- Hard Coded Questions and Display them_en.srt	
@@ -0,0 +1,948 @@
+1
+00:00:00,000 --> 00:00:03,000
+(melodic orchestral music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: Now basically we have to get the five questions hardcoded
+
+3
+00:00:06,000 --> 00:00:08,000
+so that we can play the game.
+
+4
+00:00:08,000 --> 00:00:08,000
+So let's do one thing.
+
+5
+00:00:08,000 --> 00:00:10,000
+So what I will do is I will create
+
+6
+00:00:10,000 --> 00:00:12,000
+a method called display questions, okay?
+
+7
+00:00:12,000 --> 00:00:15,000
+Because we got five questions, right?
+
+8
+00:00:15,000 --> 00:00:16,000
+I mean, that's what we are thinking now.
+
+9
+00:00:16,000 --> 00:00:18,000
+So I will say display questions, again,
+
+10
+00:00:18,000 --> 00:00:20,000
+we are not going to use this method later,
+
+11
+00:00:20,000 --> 00:00:23,000
+but at this point, let me display questions.
+
+12
+00:00:23,000 --> 00:00:25,000
+And the way you can do that is we got a method here,
+
+13
+00:00:25,000 --> 00:00:28,000
+and then we just have to call this method from the main.
+
+14
+00:00:28,000 --> 00:00:30,000
+So inside this main,
+
+15
+00:00:30,000 --> 00:00:32,000
+I need to get the object of caution service
+
+16
+00:00:32,000 --> 00:00:35,000
+because if you want to call display questions,
+
+17
+00:00:35,000 --> 00:00:38,000
+which is a part of a caution service, right?
+
+18
+00:00:38,000 --> 00:00:41,000
+So if you don't have the object for it, you can't call it.
+
+19
+00:00:41,000 --> 00:00:42,000
+So I would say question service,
+
+20
+00:00:42,000 --> 00:00:45,000
+I will say service as a variable name
+
+21
+00:00:45,000 --> 00:00:47,000
+and the new question service, right?
+
+22
+00:00:47,000 --> 00:00:51,000
+Once you got this with the help of this particular object
+
+23
+00:00:51,000 --> 00:00:54,000
+or the reference, we can simply call the display questions.
+
+24
+00:00:54,000 --> 00:00:57,000
+Now it is going to call this method, which is doing nothing.
+
+25
+00:00:57,000 --> 00:00:59,000
+But at this point, let me just print here
+
+26
+00:00:59,000 --> 00:01:01,000
+in display questions
+
+27
+00:01:01,000 --> 00:01:03,000
+so that we'll know something is happening.
+
+28
+00:01:03,000 --> 00:01:04,000
+Let's go back to main.
+
+29
+00:01:04,000 --> 00:01:05,000
+Okay, so how you run this,
+
+30
+00:01:05,000 --> 00:01:07,000
+you can simply click on this button
+
+31
+00:01:07,000 --> 00:01:10,000
+and you will get the console here, right?
+
+32
+00:01:10,000 --> 00:01:12,000
+Maybe I just want to clear the screen,
+
+33
+00:01:12,000 --> 00:01:15,000
+and also I want to keep it on the right hand side.
+
+34
+00:01:15,000 --> 00:01:18,000
+Will it be a good place? Okay, this looks good.
+
+35
+00:01:19,000 --> 00:01:20,000
+I'll just run this once again,
+
+36
+00:01:20,000 --> 00:01:21,000
+and you can see we got the output
+
+37
+00:01:21,000 --> 00:01:23,000
+which is in display question.
+
+38
+00:01:23,000 --> 00:01:26,000
+So that means we are able to run this, okay.
+
+39
+00:01:26,000 --> 00:01:28,000
+But I don't want this particular thing here.
+
+40
+00:01:28,000 --> 00:01:30,000
+What I want is I want to display question right?
+
+41
+00:01:30,000 --> 00:01:32,000
+Now how do you display each question?
+
+42
+00:01:32,000 --> 00:01:34,000
+Of course, I can print one question here.
+
+43
+00:01:34,000 --> 00:01:36,000
+Let's print one question.
+
+44
+00:01:36,000 --> 00:01:39,000
+So the way you can access that is I can say print.
+
+45
+00:01:39,000 --> 00:01:42,000
+Now since this is an array, I can say questions,
+
+46
+00:01:42,000 --> 00:01:44,000
+but it'll print the entire array, right?
+
+47
+00:01:44,000 --> 00:01:46,000
+And that's not how things works out in Java.
+
+48
+00:01:46,000 --> 00:01:50,000
+You can see, okay, let me just clear this and read on this.
+
+49
+00:01:50,000 --> 00:01:53,000
+So you can see it says something weird output here,
+
+50
+00:01:53,000 --> 00:01:53,000
+which is this.
+
+51
+00:01:53,000 --> 00:01:57,000
+So it says quad packet L and then questions.
+
+52
+00:01:57,000 --> 00:02:00,000
+The thing is if you want to print the data, okay,
+
+53
+00:02:00,000 --> 00:02:03,000
+not the array, we have to print each element,
+
+54
+00:02:03,000 --> 00:02:04,000
+because since we are printing the array,
+
+55
+00:02:04,000 --> 00:02:06,000
+that's what is doing it.
+
+56
+00:02:06,000 --> 00:02:08,000
+We need to print each element.
+
+57
+00:02:08,000 --> 00:02:10,000
+So let me print the first question.
+
+58
+00:02:10,000 --> 00:02:11,000
+Okay, so when, when you say first question,
+
+59
+00:02:11,000 --> 00:02:13,000
+that means from the array,
+
+60
+00:02:13,000 --> 00:02:14,000
+we need to get the first question,
+
+61
+00:02:14,000 --> 00:02:16,000
+and that's what we're doing here.
+
+62
+00:02:16,000 --> 00:02:18,000
+Let's run this once again.
+
+63
+00:02:18,000 --> 00:02:21,000
+And you can see now it says null, oh, that's weird.
+
+64
+00:02:21,000 --> 00:02:23,000
+Do we have question there?
+
+65
+00:02:23,000 --> 00:02:25,000
+Unfortunately, we don't have any question.
+
+66
+00:02:25,000 --> 00:02:28,000
+Example, let's say with this question here,
+
+67
+00:02:28,000 --> 00:02:31,000
+so of course the array represents one object, right?
+
+68
+00:02:31,000 --> 00:02:34,000
+So when I say question zero, it'll represent the first one,
+
+69
+00:02:34,000 --> 00:02:36,000
+not the case, because if you try to do that example,
+
+70
+00:02:36,000 --> 00:02:40,000
+if I try to get the question for a particular question,
+
+71
+00:02:40,000 --> 00:02:42,000
+so let's say we have five questions, right?
+
+72
+00:02:42,000 --> 00:02:44,000
+So if I try to fetch the question,
+
+73
+00:02:44,000 --> 00:02:47,000
+and what I know the name can be confusing,
+
+74
+00:02:47,000 --> 00:02:49,000
+but we have a question variable here,
+
+75
+00:02:49,000 --> 00:02:50,000
+which is the actual question.
+
+76
+00:02:50,000 --> 00:02:54,000
+What is Java or what's the size of anything Java?
+
+77
+00:02:54,000 --> 00:02:57,000
+So we have this here and what I will do is I will try
+
+78
+00:02:57,000 --> 00:03:00,000
+to run this call and what you will get
+
+79
+00:03:00,000 --> 00:03:02,000
+is one of the favorite thing in Java,
+
+80
+00:03:02,000 --> 00:03:03,000
+which is the null point exception.
+
+81
+00:03:03,000 --> 00:03:07,000
+Let me wrap this, let me just fit it here.
+
+82
+00:03:07,000 --> 00:03:09,000
+So you can see we got an error,
+
+83
+00:03:09,000 --> 00:03:12,000
+which is a null pointer exception.
+
+84
+00:03:12,000 --> 00:03:13,000
+The reason we got null point exception is
+
+85
+00:03:13,000 --> 00:03:16,000
+if you are thinking we got the questions, no,
+
+86
+00:03:16,000 --> 00:03:17,000
+we have not got the question,
+
+87
+00:03:17,000 --> 00:03:20,000
+but what we got is the reference of the questions,
+
+88
+00:03:20,000 --> 00:03:22,000
+not the actual object.
+
+89
+00:03:22,000 --> 00:03:25,000
+So we need to initialize those object, example.
+
+90
+00:03:25,000 --> 00:03:28,000
+If I initialize the object by saying questions
+
+91
+00:03:28,000 --> 00:03:32,000
+of zero equal to new question.
+
+92
+00:03:32,000 --> 00:03:34,000
+Now this is where I'm creating an object, okay?
+
+93
+00:03:34,000 --> 00:03:36,000
+In the initial set, which is this,
+
+94
+00:03:36,000 --> 00:03:39,000
+this is just a array of references,
+
+95
+00:03:39,000 --> 00:03:41,000
+but not the actual object.
+
+96
+00:03:41,000 --> 00:03:44,000
+And now I follow on this by clear the screen, let's run.
+
+97
+00:03:44,000 --> 00:03:45,000
+And you can see it says null,
+
+98
+00:03:45,000 --> 00:03:47,000
+so there's no null point exception, but it is null,
+
+99
+00:03:47,000 --> 00:03:49,000
+reason being we got the object,
+
+100
+00:03:49,000 --> 00:03:52,000
+but the get question is still null, okay.
+
+101
+00:03:52,000 --> 00:03:55,000
+So that means when we create the question,
+
+102
+00:03:55,000 --> 00:03:58,000
+We need to make sure that we are creating the objects of it.
+
+103
+00:03:58,000 --> 00:04:00,000
+Now how will we do it?
+
+104
+00:04:00,000 --> 00:04:01,000
+Now since we want five questions,
+
+105
+00:04:01,000 --> 00:04:03,000
+what I can do is I can create a constructor here
+
+106
+00:04:03,000 --> 00:04:05,000
+for the question service,
+
+107
+00:04:05,000 --> 00:04:08,000
+and in this we have to manually create the object.
+
+108
+00:04:08,000 --> 00:04:12,000
+So I can say questions of zero,
+
+109
+00:04:12,000 --> 00:04:13,000
+the thing which we have done here,
+
+110
+00:04:13,000 --> 00:04:15,000
+this should not be done here.
+
+111
+00:04:15,000 --> 00:04:16,000
+We should be doing that in the constructor
+
+112
+00:04:16,000 --> 00:04:18,000
+so that it'll happen only once.
+
+113
+00:04:18,000 --> 00:04:20,000
+New question.
+
+114
+00:04:20,000 --> 00:04:22,000
+And likewise, I can type this statement five times.
+
+115
+00:04:22,000 --> 00:04:25,000
+Of course, we can also use a loop there to assign
+
+116
+00:04:25,000 --> 00:04:28,000
+the values or assign the instances, okay?
+
+117
+00:04:28,000 --> 00:04:30,000
+This is the actual instance.
+
+118
+00:04:30,000 --> 00:04:32,000
+But then even if you do that,
+
+119
+00:04:32,000 --> 00:04:34,000
+your questions values will be empty, right?
+
+120
+00:04:34,000 --> 00:04:37,000
+So we have so many things to fill up, right?
+
+121
+00:04:37,000 --> 00:04:40,000
+So what we can do here is we can pass the values here
+
+122
+00:04:40,000 --> 00:04:42,000
+in the constructor for the question.
+
+123
+00:04:42,000 --> 00:04:45,000
+That also means that we need to create a constructor,
+
+124
+00:04:45,000 --> 00:04:46,000
+which will take values,
+
+125
+00:04:46,000 --> 00:04:50,000
+so I click here and say source action,
+
+126
+00:04:50,000 --> 00:04:54,000
+I need a constructor which can accept all the values.
+
+127
+00:04:54,000 --> 00:04:55,000
+Click on, okay?
+
+128
+00:04:55,000 --> 00:04:56,000
+So you can see we've got a constructor here,
+
+129
+00:04:56,000 --> 00:04:57,000
+which will take all the values
+
+130
+00:04:57,000 --> 00:04:59,000
+and then you can come back here
+
+131
+00:04:59,000 --> 00:05:01,000
+and you can put up the values here.
+
+132
+00:05:01,000 --> 00:05:02,000
+Okay, example,
+
+133
+00:05:02,000 --> 00:05:05,000
+let's say the first thing we have is question ID.
+
+134
+00:05:05,000 --> 00:05:06,000
+Then we have some question,
+
+135
+00:05:06,000 --> 00:05:08,000
+I'm not sure what the question is.
+
+136
+00:05:08,000 --> 00:05:10,000
+I will simply say what, okay?
+
+137
+00:05:10,000 --> 00:05:12,000
+And then we'll be having option one.
+
+138
+00:05:12,000 --> 00:05:15,000
+Let's say option one is A,
+
+139
+00:05:15,000 --> 00:05:17,000
+I mean the actual thing, let's say Java.
+
+140
+00:05:18,000 --> 00:05:22,000
+Then option two is Cpp, which is C++,
+
+141
+00:05:22,000 --> 00:05:24,000
+option three is Python.
+
+142
+00:05:24,000 --> 00:05:26,000
+And then so there's a question maybe,
+
+143
+00:05:26,000 --> 00:05:30,000
+which of these language is founded in year 1995,
+
+144
+00:05:30,000 --> 00:05:32,000
+so on says Java, so let's do that.
+
+145
+00:05:32,000 --> 00:05:34,000
+And the last option we are saying is C+,
+
+146
+00:05:34,000 --> 00:05:36,000
+and then we can give a right answer
+
+147
+00:05:36,000 --> 00:05:38,000
+to all these are options here, right?
+
+148
+00:05:38,000 --> 00:05:41,000
+So if we got ID question OPD, again,
+
+149
+00:05:41,000 --> 00:05:43,000
+don't get confused with this things in grade.
+
+150
+00:05:43,000 --> 00:05:46,000
+This is basically given by your VS code just
+
+151
+00:05:46,000 --> 00:05:48,000
+to make you understand what value you are assigning.
+
+152
+00:05:48,000 --> 00:05:52,000
+It'll reduce the bugs. And the last one is the answer.
+
+153
+00:05:52,000 --> 00:05:54,000
+So answer out of this is Java,
+
+154
+00:05:54,000 --> 00:05:56,000
+so we can mention Java there, right?
+
+155
+00:05:56,000 --> 00:05:58,000
+This is how we can basically create questions, okay?
+
+156
+00:05:58,000 --> 00:06:00,000
+But then we, we need to do this for five times, right?
+
+157
+00:06:00,000 --> 00:06:02,000
+So instead of typing it manually in the video,
+
+158
+00:06:02,000 --> 00:06:03,000
+I will just copy paste it, okay.
+
+159
+00:06:03,000 --> 00:06:06,000
+So I have a file somewhere sitting,
+
+160
+00:06:06,000 --> 00:06:08,000
+so I got just entered this values here,
+
+161
+00:06:08,000 --> 00:06:11,000
+so we can say we have question zero,
+
+162
+00:06:11,000 --> 00:06:13,000
+I mean, we got five questions here,
+
+163
+00:06:13,000 --> 00:06:16,000
+and then these are the values which I've inserted.
+
+164
+00:06:16,000 --> 00:06:18,000
+Nothing fancy, just a simple thing.
+
+165
+00:06:18,000 --> 00:06:20,000
+The size of a, size of double size of cache,
+
+166
+00:06:20,000 --> 00:06:22,000
+size of long size of bullion,
+
+167
+00:06:22,000 --> 00:06:23,000
+and we've got all these options here
+
+168
+00:06:23,000 --> 00:06:25,000
+with the answers of course.
+
+169
+00:06:25,000 --> 00:06:26,000
+And now let's try to display the question.
+
+170
+00:06:26,000 --> 00:06:30,000
+So now if I try to display this and if I run this code,
+
+171
+00:06:30,000 --> 00:06:31,000
+okay, let me just clear this screen.
+
+172
+00:06:31,000 --> 00:06:36,000
+So if I try to do this, compile all the files and run main,
+
+173
+00:06:40,000 --> 00:06:42,000
+yeah, this looks much better, right?
+
+174
+00:06:42,000 --> 00:06:45,000
+So instead of clicking it, it gives the bunch of text,
+
+175
+00:06:45,000 --> 00:06:46,000
+let's do this.
+
+176
+00:06:46,000 --> 00:06:48,000
+So you can see when when I run this main,
+
+177
+00:06:48,000 --> 00:06:50,000
+it is giving me size of ink, okay?
+
+178
+00:06:50,000 --> 00:06:52,000
+So we got the first question,
+
+179
+00:06:52,000 --> 00:06:53,000
+but I want to print all the questions, right?
+
+180
+00:06:53,000 --> 00:06:55,000
+How will you do that?
+
+181
+00:06:55,000 --> 00:06:58,000
+So what I can do here is I will use a loop
+
+182
+00:06:58,000 --> 00:06:59,000
+to print all the values,
+
+183
+00:06:59,000 --> 00:07:02,000
+or maybe I can use the enhance follow loop,
+
+184
+00:07:02,000 --> 00:07:03,000
+which we have seen.
+
+185
+00:07:03,000 --> 00:07:07,000
+So I can say question Q, colon questions.
+
+186
+00:07:07,000 --> 00:07:08,000
+So question Q from questions,
+
+187
+00:07:08,000 --> 00:07:12,000
+and then I can open the curly package packets,
+
+188
+00:07:12,000 --> 00:07:13,000
+close it here, okay?
+
+189
+00:07:13,000 --> 00:07:15,000
+And now instead of printing this get question,
+
+190
+00:07:15,000 --> 00:07:18,000
+I want to print, or maybe I can just print get question.
+
+191
+00:07:18,000 --> 00:07:19,000
+The only thing is instead of saying zero here,
+
+192
+00:07:19,000 --> 00:07:21,000
+we should be saying Q now.
+
+193
+00:07:21,000 --> 00:07:23,000
+Because every time you run this loop,
+
+194
+00:07:23,000 --> 00:07:24,000
+the enhanced follow loop,
+
+195
+00:07:24,000 --> 00:07:27,000
+basically it'll take one question from the questions
+
+196
+00:07:27,000 --> 00:07:28,000
+and put it in the queue.
+
+197
+00:07:28,000 --> 00:07:30,000
+So we can say q.getQuestion, right?
+
+198
+00:07:30,000 --> 00:07:33,000
+So in the loop it'll run five times
+
+199
+00:07:33,000 --> 00:07:36,000
+and you will get five questions basically,
+
+200
+00:07:36,000 --> 00:07:37,000
+I dunno why I'm using this.
+
+201
+00:07:37,000 --> 00:07:39,000
+Let me just use this.
+
+202
+00:07:39,000 --> 00:07:41,000
+Compile all the files and run main,
+
+203
+00:07:41,000 --> 00:07:43,000
+and you can see we got all the questions,
+
+204
+00:07:43,000 --> 00:07:45,000
+but what if you want to print
+
+205
+00:07:45,000 --> 00:07:48,000
+the question, options, answer as well?
+
+206
+00:07:48,000 --> 00:07:50,000
+So what I can do is instead of printing the get question,
+
+207
+00:07:50,000 --> 00:07:53,000
+let me print the queue itself.
+
+208
+00:07:53,000 --> 00:07:55,000
+Now the problem is when you do this,
+
+209
+00:07:55,000 --> 00:07:57,000
+let me compile all the files again
+
+210
+00:07:57,000 --> 00:08:01,000
+and one, it'll print the question and some weird stuff.
+
+211
+00:08:01,000 --> 00:08:04,000
+It's just that if you want to print the object,
+
+212
+00:08:04,000 --> 00:08:06,000
+we have to use two string method.
+
+213
+00:08:06,000 --> 00:08:09,000
+So I can go back to my question and question
+
+214
+00:08:09,000 --> 00:08:13,000
+what we don't have in the question is a two stringing.
+
+215
+00:08:13,000 --> 00:08:14,000
+So I can right click here
+
+216
+00:08:14,000 --> 00:08:17,000
+and source action, generate two string.
+
+217
+00:08:17,000 --> 00:08:19,000
+So what two stringing will do is every time
+
+218
+00:08:19,000 --> 00:08:21,000
+we try to print the object,
+
+219
+00:08:21,000 --> 00:08:24,000
+it'll call the two stringing method, which is printing what?
+
+220
+00:08:24,000 --> 00:08:28,000
+So two basically prints the data in a particular format,
+
+221
+00:08:28,000 --> 00:08:30,000
+which is generated by the ID.
+
+222
+00:08:30,000 --> 00:08:32,000
+Of course you can type it manually as well,
+
+223
+00:08:32,000 --> 00:08:33,000
+that's your choice.
+
+224
+00:08:33,000 --> 00:08:34,000
+Now, after making the changes,
+
+225
+00:08:34,000 --> 00:08:37,000
+if I go back and compile this two,
+
+226
+00:08:37,000 --> 00:08:40,000
+run, and now you can see we got all the questions.
+
+227
+00:08:40,000 --> 00:08:42,000
+So we got question, question ID,
+
+228
+00:08:42,000 --> 00:08:46,000
+the actual question then options
+
+229
+00:08:46,000 --> 00:08:48,000
+four options and answer, right?
+
+230
+00:08:48,000 --> 00:08:50,000
+So at this point what we were able to do is we were able
+
+231
+00:08:50,000 --> 00:08:54,000
+to generate the questions, five questions here,
+
+232
+00:08:54,000 --> 00:08:55,000
+the hard coding way,
+
+233
+00:08:55,000 --> 00:08:58,000
+and then we were able to display the questions.
+
+234
+00:08:58,000 --> 00:08:59,000
+Now in the next video,
+
+235
+00:08:59,000 --> 00:09:01,000
+let's try to do something where a user can play the game,
+
+236
+00:09:01,000 --> 00:09:05,000
+at least a user can see the questions one by one.
+
+237
+00:09:05,000 --> 00:09:07,000
+Let's try do that in the upcoming videos.
+
diff --git a/03 - Advance Java/003 Source-Code.url b/03 - Advance Java/003 Source-Code.url
new file mode 100644
index 0000000000000000000000000000000000000000..4c695cf501825d447ed987531cc3845423d626b8
--- /dev/null
+++ b/03 - Advance Java/003 Source-Code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/Gaurav560/quiz-console-app
\ No newline at end of file
diff --git a/03 - Advance Java/004 Project 1- Play Quiz_en.srt b/03 - Advance Java/004 Project 1- Play Quiz_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..ad2bea53af7d06b6b762b8e4c07eb4ee4d016a9b
--- /dev/null
+++ b/03 - Advance Java/004 Project 1- Play Quiz_en.srt	
@@ -0,0 +1,604 @@
+1
+00:00:00,000 --> 00:00:02,000
+(gentle music)
+
+2
+00:00:02,000 --> 00:00:04,000
+-: Now, basically we were able
+
+3
+00:00:04,000 --> 00:00:05,000
+to display the questions right?
+
+4
+00:00:05,000 --> 00:00:07,000
+Now it's time to play the quiz.
+
+5
+00:00:07,000 --> 00:00:08,000
+Now in the play the quiz,
+
+6
+00:00:08,000 --> 00:00:11,000
+what will happen is we will create a method,
+
+7
+00:00:11,000 --> 00:00:14,000
+which will display the questions, okay, not this one,
+
+8
+00:00:14,000 --> 00:00:15,000
+but it'll display the question.
+
+9
+00:00:15,000 --> 00:00:17,000
+And also for every question,
+
+10
+00:00:17,000 --> 00:00:20,000
+it'll take the input from the user.
+
+11
+00:00:20,000 --> 00:00:22,000
+What is their choice, right? What is their answer?
+
+12
+00:00:22,000 --> 00:00:23,000
+Now how do we do that?
+
+13
+00:00:23,000 --> 00:00:25,000
+So basically we can change
+
+14
+00:00:25,000 --> 00:00:26,000
+the display question itself.
+
+15
+00:00:26,000 --> 00:00:27,000
+Instead of saying display question,
+
+16
+00:00:27,000 --> 00:00:31,000
+I can say play quiz, right?
+
+17
+00:00:31,000 --> 00:00:33,000
+This will make much more sense, right? Play quiz.
+
+18
+00:00:33,000 --> 00:00:36,000
+And then, okay, also we need to change it here now.
+
+19
+00:00:36,000 --> 00:00:38,000
+We can't say display questions,
+
+20
+00:00:38,000 --> 00:00:40,000
+the method name has been changed.
+
+21
+00:00:41,000 --> 00:00:45,000
+So just play.quiz, right? And now go back here.
+
+22
+00:00:45,000 --> 00:00:47,000
+Now when you are playing quiz, you don't need
+
+23
+00:00:47,000 --> 00:00:48,000
+to just display the question, right?
+
+24
+00:00:48,000 --> 00:00:51,000
+We need to display the question, but not in this format.
+
+25
+00:00:51,000 --> 00:00:53,000
+It is printing all the question.
+
+26
+00:00:53,000 --> 00:00:55,000
+And after printing one question,
+
+27
+00:00:55,000 --> 00:00:59,000
+it should also ask the user what is their answer, right?
+
+28
+00:00:59,000 --> 00:01:01,000
+Okay, so what I'm saying is instead of printing
+
+29
+00:01:01,000 --> 00:01:04,000
+the entire question, I will print this one by one.
+
+30
+00:01:04,000 --> 00:01:07,000
+Maybe the first thing I'm going to print is the ID,
+
+31
+00:01:07,000 --> 00:01:09,000
+because I want to print the ID as well.
+
+32
+00:01:09,000 --> 00:01:13,000
+The only thing is when I say ID, maybe I want to
+
+33
+00:01:13,000 --> 00:01:16,000
+print because the ID number starts with one okay?
+
+34
+00:01:16,000 --> 00:01:17,000
+That's what we're doing here.
+
+35
+00:01:17,000 --> 00:01:19,000
+Yeah, we have ID number one that works.
+
+36
+00:01:19,000 --> 00:01:21,000
+I can simply say, getID.
+
+37
+00:01:21,000 --> 00:01:22,000
+It'll print the ID first
+
+38
+00:01:22,000 --> 00:01:27,000
+and maybe instead of printing just this, I will also print
+
+39
+00:01:27,000 --> 00:01:29,000
+question number so that our user will know
+
+40
+00:01:29,000 --> 00:01:31,000
+what we are printing.
+
+41
+00:01:31,000 --> 00:01:33,000
+So question number, it'll print the ID.
+
+42
+00:01:33,000 --> 00:01:35,000
+And then the next line, on the next line,
+
+43
+00:01:35,000 --> 00:01:37,000
+I want to print the actual question.
+
+44
+00:01:37,000 --> 00:01:42,000
+So I will say q.get question, that's done.
+
+45
+00:01:43,000 --> 00:01:45,000
+And then on the next line, I want to print the options,
+
+46
+00:01:45,000 --> 00:01:46,000
+all four options.
+
+47
+00:01:46,000 --> 00:01:51,000
+So I can say, print out, this is not print, q.getOpt1.
+
+48
+00:01:53,000 --> 00:01:56,000
+And likewise, I want to do this for four options.
+
+49
+00:01:56,000 --> 00:01:58,000
+I can simply, you know, creating array will make
+
+50
+00:01:58,000 --> 00:02:01,000
+much more sense for the options.
+
+51
+00:02:01,000 --> 00:02:03,000
+We can use inner loop to print all the options, right?
+
+52
+00:02:03,000 --> 00:02:04,000
+You can do that.
+
+53
+00:02:04,000 --> 00:02:07,000
+Maybe that is one of your assignment.
+
+54
+00:02:07,000 --> 00:02:10,000
+You can try it out. So three and four, okay?
+
+55
+00:02:10,000 --> 00:02:13,000
+So what we are displaying is we are displaying a question.
+
+56
+00:02:13,000 --> 00:02:15,000
+I mean we are displaying the question ID here,
+
+57
+00:02:15,000 --> 00:02:17,000
+then the actual question and the four options.
+
+58
+00:02:17,000 --> 00:02:20,000
+And after this we need to display, okay?
+
+59
+00:02:20,000 --> 00:02:23,000
+Make sure that you are not displaying the answer.
+
+60
+00:02:23,000 --> 00:02:25,000
+So let's keep that, because here if you can see the earlier
+
+61
+00:02:25,000 --> 00:02:27,000
+output it was displaying the answer as well.
+
+62
+00:02:27,000 --> 00:02:29,000
+Don't display the answers.
+
+63
+00:02:29,000 --> 00:02:31,000
+But after showing this question,
+
+64
+00:02:31,000 --> 00:02:33,000
+I want to take the user input.
+
+65
+00:02:33,000 --> 00:02:34,000
+Now, how do you take user input?
+
+66
+00:02:34,000 --> 00:02:36,000
+So we can use something called scanner.
+
+67
+00:02:36,000 --> 00:02:39,000
+So I can say scanner sc = new scanner.
+
+68
+00:02:40,000 --> 00:02:43,000
+And in this scanner you can pass two things,
+
+69
+00:02:43,000 --> 00:02:44,000
+not two things, one.
+
+70
+00:02:44,000 --> 00:02:46,000
+You can pass System.in.
+
+71
+00:02:46,000 --> 00:02:48,000
+So basically what you're doing is you're saying,
+
+72
+00:02:48,000 --> 00:02:51,000
+"Hey, I want to get the input from the user,"
+
+73
+00:02:51,000 --> 00:02:53,000
+and the input will be coming from the input
+
+74
+00:02:53,000 --> 00:02:55,000
+source, which is System.in.
+
+75
+00:02:55,000 --> 00:02:56,000
+So the way we are doing it here, right,
+
+76
+00:02:56,000 --> 00:02:58,000
+we are saying System.out, which is for the output.
+
+77
+00:02:58,000 --> 00:03:01,000
+System.in is for the input.
+
+78
+00:03:01,000 --> 00:03:04,000
+And scanner helps you to get the value
+
+79
+00:03:04,000 --> 00:03:06,000
+because scanner had a lot of methods to use.
+
+80
+00:03:06,000 --> 00:03:07,000
+And one thing to remember,
+
+81
+00:03:07,000 --> 00:03:09,000
+whenever we use scanner, we have to import a package,
+
+82
+00:03:09,000 --> 00:03:13,000
+which is java.util.scanner because it's a inbuilt class.
+
+83
+00:03:13,000 --> 00:03:16,000
+And if you want to use it, you have to just import it, okay?
+
+84
+00:03:16,000 --> 00:03:19,000
+Otherwise, in your IDE, if you complete the word scanner,
+
+85
+00:03:19,000 --> 00:03:23,000
+say Ctrl + space, it'll give you the input option.
+
+86
+00:03:23,000 --> 00:03:25,000
+Okay once you've got this scanner,
+
+87
+00:03:25,000 --> 00:03:26,000
+now we can take the input.
+
+88
+00:03:26,000 --> 00:03:30,000
+The way you can take the input is sc.nextLine.
+
+89
+00:03:30,000 --> 00:03:31,000
+So with the help of next line, whatever,
+
+90
+00:03:31,000 --> 00:03:35,000
+a user has written on the console, it'll take that
+
+91
+00:03:35,000 --> 00:03:38,000
+as a input and you can store that somewhere now.
+
+92
+00:03:38,000 --> 00:03:39,000
+Where you want to store it,
+
+93
+00:03:39,000 --> 00:03:41,000
+maybe I will use a variable here.
+
+94
+00:03:41,000 --> 00:03:44,000
+Let's say selection, the user selection,
+
+95
+00:03:44,000 --> 00:03:47,000
+and then, okay, I need to create this variable somewhere.
+
+96
+00:03:47,000 --> 00:03:49,000
+We'll do that later, but I will take the input
+
+97
+00:03:49,000 --> 00:03:52,000
+and store it in a selection as a variable.
+
+98
+00:03:52,000 --> 00:03:54,000
+So whatever user selected.
+
+99
+00:03:54,000 --> 00:03:58,000
+But the problem here is this loop will run for five times,
+
+100
+00:03:58,000 --> 00:04:01,000
+and every time you do this, it'll change the value, right?
+
+101
+00:04:01,000 --> 00:04:02,000
+It'll keep changing the value
+
+102
+00:04:02,000 --> 00:04:05,000
+with the new value which a user inserted.
+
+103
+00:04:05,000 --> 00:04:06,000
+So instead of creating one variable,
+
+104
+00:04:06,000 --> 00:04:08,000
+it should be an array itself.
+
+105
+00:04:08,000 --> 00:04:13,000
+So I can say string selection,
+
+106
+00:04:13,000 --> 00:04:16,000
+and this will be an array of five values, right?
+
+107
+00:04:16,000 --> 00:04:20,000
+So it'll be five, new string five, okay?
+
+108
+00:04:20,000 --> 00:04:24,000
+So we got an array of five values here as you can see.
+
+109
+00:04:26,000 --> 00:04:30,000
+And if I go back now, instead of storing it in selection,
+
+110
+00:04:30,000 --> 00:04:33,000
+we should store in a particular index.
+
+111
+00:04:33,000 --> 00:04:34,000
+Now, how do we know the index?
+
+112
+00:04:34,000 --> 00:04:36,000
+The problem is we are using an enhanced forloop.
+
+113
+00:04:36,000 --> 00:04:39,000
+That's why we don't have an I.
+
+114
+00:04:39,000 --> 00:04:43,000
+So what I can do is I can say int i=0 initially,
+
+115
+00:04:43,000 --> 00:04:46,000
+and here I can simply say i++.
+
+116
+00:04:46,000 --> 00:04:48,000
+Either you can say i++ here,
+
+117
+00:04:48,000 --> 00:04:50,000
+or maybe you can just to keep it simple, I can say
+
+118
+00:04:50,000 --> 00:04:52,000
+i and then i++.
+
+119
+00:04:52,000 --> 00:04:55,000
+Because every time you run this loop, we have to make sure
+
+120
+00:04:55,000 --> 00:04:58,000
+that the new answer is going to the next index.
+
+121
+00:04:58,000 --> 00:05:00,000
+So whatever a user is entering
+
+122
+00:05:00,000 --> 00:05:02,000
+that is going into the selection.
+
+123
+00:05:02,000 --> 00:05:05,000
+And maybe I want to display the entire selection
+
+124
+00:05:05,000 --> 00:05:09,000
+what user has entered, just to see right
+
+125
+00:05:09,000 --> 00:05:11,000
+how things are working out.
+
+126
+00:05:11,000 --> 00:05:15,000
+So I can use a loop here, I can say string s from
+
+127
+00:05:16,000 --> 00:05:19,000
+selection, and I can print each s.
+
+128
+00:05:19,000 --> 00:05:23,000
+So it'll print all the user answers, what users entered.
+
+129
+00:05:23,000 --> 00:05:25,000
+I think this looks cool.
+
+130
+00:05:25,000 --> 00:05:27,000
+Let me just clear this screen
+
+131
+00:05:27,000 --> 00:05:30,000
+and compile the file, all the files,
+
+132
+00:05:30,000 --> 00:05:35,000
+basically whatever you have changed and run this.
+
+133
+00:05:35,000 --> 00:05:38,000
+And you can see it says, now you got the question right?
+
+134
+00:05:38,000 --> 00:05:41,000
+Question number one, size of int,
+
+135
+00:05:41,000 --> 00:05:43,000
+these are the four options you got.
+
+136
+00:05:43,000 --> 00:05:44,000
+You have to enter the right answer.
+
+137
+00:05:46,000 --> 00:05:48,000
+So let's say four in this case, enter.
+
+138
+00:05:48,000 --> 00:05:52,000
+Second question, size of double is eight character.
+
+139
+00:05:52,000 --> 00:05:54,000
+Let me give some wrong answer.
+
+140
+00:05:54,000 --> 00:05:58,000
+Long, just enter anything you want
+
+141
+00:05:58,000 --> 00:06:00,000
+because at this point we are just displaying it, right?
+
+142
+00:06:00,000 --> 00:06:05,000
+And at the end, you can see this is what user has entered.
+
+143
+00:06:05,000 --> 00:06:07,000
+So for the first question, user has entered four,
+
+144
+00:06:07,000 --> 00:06:11,000
+then eight, then eight, then two, then three, right?
+
+145
+00:06:11,000 --> 00:06:13,000
+So yeah, so till this point, we were able
+
+146
+00:06:13,000 --> 00:06:17,000
+to display the questions one by one and get the user input.
+
+147
+00:06:17,000 --> 00:06:21,000
+That's what we have done here. Cool.
+
+148
+00:06:21,000 --> 00:06:24,000
+But then how will you check if the user has
+
+149
+00:06:24,000 --> 00:06:26,000
+entered it correctly or not?
+
+150
+00:06:26,000 --> 00:06:28,000
+Or maybe you want to display this call.
+
+151
+00:06:28,000 --> 00:06:31,000
+How will you do that? Let's do that in the next video.
+
diff --git a/03 - Advance Java/004 Source-Code.url b/03 - Advance Java/004 Source-Code.url
new file mode 100644
index 0000000000000000000000000000000000000000..4c695cf501825d447ed987531cc3845423d626b8
--- /dev/null
+++ b/03 - Advance Java/004 Source-Code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/Gaurav560/quiz-console-app
\ No newline at end of file
diff --git a/03 - Advance Java/005 Source-Code.url b/03 - Advance Java/005 Source-Code.url
new file mode 100644
index 0000000000000000000000000000000000000000..4c695cf501825d447ed987531cc3845423d626b8
--- /dev/null
+++ b/03 - Advance Java/005 Source-Code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/Gaurav560/quiz-console-app
\ No newline at end of file
diff --git a/03 - Advance Java/006 Abstract keyword_en.srt b/03 - Advance Java/006 Abstract keyword_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..2d51a7c7f395ddd915fc945e8b73880a119c9ec1
--- /dev/null
+++ b/03 - Advance Java/006 Abstract keyword_en.srt	
@@ -0,0 +1,1304 @@
+1
+00:00:00,000 --> 00:00:03,000
+(light piano music)
+
+2
+00:00:03,000 --> 00:00:06,000
+-: In this video, let's talk about abstract keyword.
+
+3
+00:00:06,000 --> 00:00:07,000
+Now, what is abstract?
+
+4
+00:00:07,000 --> 00:00:09,000
+So before that, let's understand something,
+
+5
+00:00:09,000 --> 00:00:11,000
+so we know what is class,
+
+6
+00:00:11,000 --> 00:00:12,000
+what is object, what is inheritance,
+
+7
+00:00:12,000 --> 00:00:15,000
+and how do we do overriding of the methods, right?
+
+8
+00:00:15,000 --> 00:00:16,000
+Now, with those knowledge,
+
+9
+00:00:16,000 --> 00:00:18,000
+let's talk about abstract keyword.
+
+10
+00:00:18,000 --> 00:00:21,000
+So for that, what I will do is I will create a class here,
+
+11
+00:00:21,000 --> 00:00:24,000
+and let me name this class as let's say, a car.
+
+12
+00:00:24,000 --> 00:00:26,000
+Okay? Now, in this car you will define some methods.
+
+13
+00:00:26,000 --> 00:00:28,000
+Let's say, if we talk about car,
+
+14
+00:00:28,000 --> 00:00:32,000
+a car can drive, of course, right?
+
+15
+00:00:32,000 --> 00:00:35,000
+A car can play music as well, public void.
+
+16
+00:00:35,000 --> 00:00:37,000
+I mean, that's what we do, right?
+
+17
+00:00:37,000 --> 00:00:39,000
+We also play music in the car.
+
+18
+00:00:39,000 --> 00:00:40,000
+You know, some people, they don't start their car
+
+19
+00:00:40,000 --> 00:00:45,000
+before playing the music or they don't set it
+
+20
+00:00:45,000 --> 00:00:48,000
+on a drive mode before they play the music.
+
+21
+00:00:48,000 --> 00:00:49,000
+Okay, so we have these two methods, let's say,
+
+22
+00:00:49,000 --> 00:00:51,000
+or maybe we can add some more methods in the car.
+
+23
+00:00:51,000 --> 00:00:54,000
+Maybe you can sleep in your car and other methods.
+
+24
+00:00:54,000 --> 00:00:56,000
+But let's say, we have these two,
+
+25
+00:00:56,000 --> 00:00:58,000
+we have drive and we have playMusic.
+
+26
+00:00:58,000 --> 00:01:01,000
+And of course, in this method, I can define some statements.
+
+27
+00:01:01,000 --> 00:01:03,000
+Let's say, when I say it is playing music,
+
+28
+00:01:03,000 --> 00:01:06,000
+I can say, play music or we can write multiple statements.
+
+29
+00:01:06,000 --> 00:01:08,000
+Logic is not important. The important thing is the concept.
+
+30
+00:01:08,000 --> 00:01:09,000
+Let's focus on that.
+
+31
+00:01:09,000 --> 00:01:12,000
+So let's say in the play music, we have this statement.
+
+32
+00:01:12,000 --> 00:01:15,000
+And in drive, let's say, at this point, I'm not sure I want
+
+33
+00:01:15,000 --> 00:01:18,000
+to build my own car, but I'm not sure how can I drive a car?
+
+34
+00:01:18,000 --> 00:01:20,000
+I know how to implement play music,
+
+35
+00:01:20,000 --> 00:01:22,000
+but I don't know how to set up the engine.
+
+36
+00:01:22,000 --> 00:01:23,000
+I'm manufacturing my own car.
+
+37
+00:01:23,000 --> 00:01:25,000
+So I don't know how to set up the engine,
+
+38
+00:01:25,000 --> 00:01:28,000
+how to set up the wheels, but a car should drive.
+
+39
+00:01:28,000 --> 00:01:31,000
+That's what I know and that's why we call it a car, right?
+
+40
+00:01:31,000 --> 00:01:32,000
+If you don't have a drive feature,
+
+41
+00:01:32,000 --> 00:01:34,000
+then why you will call it a car?
+
+42
+00:01:34,000 --> 00:01:36,000
+You can state it's a home theater.
+
+43
+00:01:36,000 --> 00:01:39,000
+Anyway, now, if I want to use this car,
+
+44
+00:01:39,000 --> 00:01:41,000
+I can simply create an object.
+
+45
+00:01:41,000 --> 00:01:44,000
+I can say, a car obj = new Car.
+
+46
+00:01:44,000 --> 00:01:45,000
+And then I can call the methods.
+
+47
+00:01:45,000 --> 00:01:50,000
+I can call both the methods, obj.drive and obj.playMusic.
+
+48
+00:01:52,000 --> 00:01:53,000
+Of course, we have two methods,
+
+49
+00:01:53,000 --> 00:01:55,000
+I should be able to call them.
+
+50
+00:01:55,000 --> 00:01:56,000
+Now, if you observe, in the drive,
+
+51
+00:01:56,000 --> 00:01:58,000
+we are not doing anything. Why we are not doing anything?
+
+52
+00:01:58,000 --> 00:02:01,000
+Because I don't know how to implement drive,
+
+53
+00:02:01,000 --> 00:02:02,000
+but I know how to implement playMusic.
+
+54
+00:02:02,000 --> 00:02:04,000
+So I'm able to create this object,
+
+55
+00:02:04,000 --> 00:02:06,000
+and I'm able to call these two methods
+
+56
+00:02:06,000 --> 00:02:08,000
+and I think it should work.
+
+57
+00:02:08,000 --> 00:02:10,000
+And if I go back and run, it works.
+
+58
+00:02:10,000 --> 00:02:12,000
+It's not like if you don't define something,
+
+59
+00:02:12,000 --> 00:02:13,000
+it will not work.
+
+60
+00:02:13,000 --> 00:02:14,000
+It's working.
+
+61
+00:02:14,000 --> 00:02:17,000
+The only thing is when you're defining this method,
+
+62
+00:02:17,000 --> 00:02:20,000
+you are actually not implementing anything here.
+
+63
+00:02:20,000 --> 00:02:21,000
+You're not writing any statements.
+
+64
+00:02:21,000 --> 00:02:23,000
+So it's valid in Javas and text term,
+
+65
+00:02:23,000 --> 00:02:25,000
+but as a feature, I mean,
+
+66
+00:02:25,000 --> 00:02:26,000
+just imagine you're buying a new phone,
+
+67
+00:02:26,000 --> 00:02:29,000
+and your phone says it can do this feature, this feature,
+
+68
+00:02:29,000 --> 00:02:31,000
+feature one, feature two, feature three,
+
+69
+00:02:31,000 --> 00:02:32,000
+but then none of the feature works.
+
+70
+00:02:32,000 --> 00:02:35,000
+Of course, you will not buy any phone like that, right?
+
+71
+00:02:35,000 --> 00:02:37,000
+In the same way, if we talk about this car,
+
+72
+00:02:37,000 --> 00:02:38,000
+you are writing a method over here,
+
+73
+00:02:38,000 --> 00:02:41,000
+which is drive when you're not implementing it.
+
+74
+00:02:41,000 --> 00:02:43,000
+Why someone should be able to create object of this?
+
+75
+00:02:43,000 --> 00:02:45,000
+Why in first place,
+
+76
+00:02:45,000 --> 00:02:47,000
+someone should create a class itself, right?
+
+77
+00:02:47,000 --> 00:02:49,000
+When you don't know how to implement it.
+
+78
+00:02:49,000 --> 00:02:51,000
+See, the thing is when you build an application,
+
+79
+00:02:51,000 --> 00:02:53,000
+you have a structure which you follow.
+
+80
+00:02:53,000 --> 00:02:55,000
+You design your application.
+
+81
+00:02:55,000 --> 00:02:56,000
+I'm not talking about the thing
+
+82
+00:02:56,000 --> 00:02:57,000
+which you see on the screen.
+
+83
+00:02:57,000 --> 00:02:59,000
+I'm talking about when you build an application,
+
+84
+00:02:59,000 --> 00:03:00,000
+you design on paper.
+
+85
+00:03:00,000 --> 00:03:01,000
+What are the classes you need?
+
+86
+00:03:01,000 --> 00:03:03,000
+What are the methods you need?
+
+87
+00:03:03,000 --> 00:03:06,000
+Now, at this point, you know how to play music,
+
+88
+00:03:06,000 --> 00:03:08,000
+but you don't know how to drive.
+
+89
+00:03:08,000 --> 00:03:11,000
+Now, in that case, should I remove this method completely?
+
+90
+00:03:11,000 --> 00:03:14,000
+If I do that, then how will you call it as a car?
+
+91
+00:03:14,000 --> 00:03:15,000
+So what you can do is you can say,
+
+92
+00:03:15,000 --> 00:03:18,000
+hey, you know, I'm creating this method drive,
+
+93
+00:03:18,000 --> 00:03:22,000
+but I'm not sure what should I implement it here?
+
+94
+00:03:22,000 --> 00:03:24,000
+So instead of defining it here,
+
+95
+00:03:24,000 --> 00:03:25,000
+so when you open the curly brackets and close,
+
+96
+00:03:25,000 --> 00:03:27,000
+you are basically defining a method.
+
+97
+00:03:27,000 --> 00:03:29,000
+So instead of defining a method,
+
+98
+00:03:29,000 --> 00:03:31,000
+you can basically declare a method,
+
+99
+00:03:31,000 --> 00:03:34,000
+which means you can put a semicolon at the end.
+
+100
+00:03:34,000 --> 00:03:37,000
+When you do that, you are declaring a method.
+
+101
+00:03:37,000 --> 00:03:40,000
+That also means that the drive feature you had declaring
+
+102
+00:03:40,000 --> 00:03:42,000
+but it is not working and no one should be able
+
+103
+00:03:42,000 --> 00:03:44,000
+to create object of it, okay?
+
+104
+00:03:44,000 --> 00:03:45,000
+Again, we'll see that in some time,
+
+105
+00:03:45,000 --> 00:03:48,000
+but when I declare it, it is giving you an error.
+
+106
+00:03:48,000 --> 00:03:49,000
+Now, first of all, why you will declare it
+
+107
+00:03:49,000 --> 00:03:51,000
+when you are not defining anything?
+
+108
+00:03:51,000 --> 00:03:55,000
+Maybe I have this mindset, someone else can just come back,
+
+109
+00:03:55,000 --> 00:03:57,000
+and they can say they can implement a car.
+
+110
+00:03:57,000 --> 00:04:01,000
+Maybe they will build a wagon, let's say,
+
+111
+00:04:01,000 --> 00:04:04,000
+and a wagon will extend my car
+
+112
+00:04:04,000 --> 00:04:06,000
+and it is the wagon's responsibility.
+
+113
+00:04:06,000 --> 00:04:08,000
+In fact, you know, instead of saying wagon,
+
+114
+00:04:08,000 --> 00:04:09,000
+let's say, WagonR.
+
+115
+00:04:09,000 --> 00:04:11,000
+It's a very famous car if you search online.
+
+116
+00:04:12,000 --> 00:04:16,000
+So we have this WagonR car which some of them don't like,
+
+117
+00:04:16,000 --> 00:04:18,000
+not a big fan of it, but okay,
+
+118
+00:04:19,000 --> 00:04:21,000
+so let's say we have this car WagonR extends Car.
+
+119
+00:04:21,000 --> 00:04:23,000
+In fact, I have a car which is smaller
+
+120
+00:04:23,000 --> 00:04:26,000
+than WagonR which I love.
+
+121
+00:04:26,000 --> 00:04:29,000
+So we have this class, WagonR extends Car here.
+
+122
+00:04:29,000 --> 00:04:32,000
+And what I want here is I want this WagonR
+
+123
+00:04:32,000 --> 00:04:34,000
+to implement the drive feature.
+
+124
+00:04:34,000 --> 00:04:37,000
+See, if you think car is just an abstract concept, right?
+
+125
+00:04:37,000 --> 00:04:38,000
+No one actually buys a car.
+
+126
+00:04:38,000 --> 00:04:43,000
+What you buy is a real car, like WagonR or BMW GLS
+
+127
+00:04:43,000 --> 00:04:47,000
+or Toyota Fortuner or Ford EcoSport, right?
+
+128
+00:04:47,000 --> 00:04:49,000
+So you buy a real car. You don't buy a car.
+
+129
+00:04:49,000 --> 00:04:51,000
+This is just a concept.
+
+130
+00:04:51,000 --> 00:04:52,000
+So when I say drive here,
+
+131
+00:04:52,000 --> 00:04:53,000
+a car don't know how to drive,
+
+132
+00:04:53,000 --> 00:04:56,000
+but then when you create a real car,
+
+133
+00:04:56,000 --> 00:04:58,000
+that car will know how to drive.
+
+134
+00:04:58,000 --> 00:05:01,000
+So I want this WagonR to be responsible
+
+135
+00:05:01,000 --> 00:05:02,000
+to define this method.
+
+136
+00:05:02,000 --> 00:05:05,000
+Okay, so, I can just copy this and paste it here.
+
+137
+00:05:05,000 --> 00:05:07,000
+And here, instead of declaring it, I will define.
+
+138
+00:05:07,000 --> 00:05:11,000
+So what I want is I want this WagonR to implement it.
+
+139
+00:05:11,000 --> 00:05:13,000
+Of course, the other feature like play music
+
+140
+00:05:13,000 --> 00:05:16,000
+can simply be extended, but not drive.
+
+141
+00:05:16,000 --> 00:05:18,000
+Drive should be implemented here.
+
+142
+00:05:18,000 --> 00:05:22,000
+And WagonR, I mean the company who built WagonR cars,
+
+143
+00:05:22,000 --> 00:05:26,000
+it's their responsibility to define the method here.
+
+144
+00:05:26,000 --> 00:05:27,000
+I can say driving, of course,
+
+145
+00:05:27,000 --> 00:05:29,000
+they will write a complex logic,
+
+146
+00:05:29,000 --> 00:05:31,000
+but just to make it simple, I'm writing one statement.
+
+147
+00:05:31,000 --> 00:05:34,000
+So they're responsible to define this method,
+
+148
+00:05:34,000 --> 00:05:35,000
+and we're not doing it here.
+
+149
+00:05:35,000 --> 00:05:37,000
+Now, if you want to declare a method,
+
+150
+00:05:37,000 --> 00:05:39,000
+you can see we are getting an error here,
+
+151
+00:05:39,000 --> 00:05:41,000
+you can use an abstract keyword.
+
+152
+00:05:41,000 --> 00:05:42,000
+So when you say abstract,
+
+153
+00:05:42,000 --> 00:05:46,000
+it means I'm just giving you the abstract idea
+
+154
+00:05:46,000 --> 00:05:48,000
+of a car should have a drive feature,
+
+155
+00:05:48,000 --> 00:05:50,000
+but I don't know how to implement it.
+
+156
+00:05:50,000 --> 00:05:52,000
+Now, when you are using my feature
+
+157
+00:05:52,000 --> 00:05:55,000
+and when you call your vehicle as a car,
+
+158
+00:05:55,000 --> 00:05:57,000
+it should have a drive feature.
+
+159
+00:05:57,000 --> 00:05:59,000
+Or whatever object you're creating is a car,
+
+160
+00:05:59,000 --> 00:06:01,000
+you need to have a drive feature,
+
+161
+00:06:01,000 --> 00:06:02,000
+and that's how you make it.
+
+162
+00:06:02,000 --> 00:06:05,000
+So you make a public abstract void drive.
+
+163
+00:06:05,000 --> 00:06:07,000
+So you have to use an abstract keyboard
+
+164
+00:06:07,000 --> 00:06:09,000
+if you want to declare a method, okay?
+
+165
+00:06:09,000 --> 00:06:11,000
+Here we are defining it,
+
+166
+00:06:11,000 --> 00:06:13,000
+but if you can see, even if I do abstract,
+
+167
+00:06:13,000 --> 00:06:15,000
+it is giving you an error.
+
+168
+00:06:15,000 --> 00:06:18,000
+It says, the abstract method drive in type Car
+
+169
+00:06:18,000 --> 00:06:20,000
+can only be defined by an abstract class.
+
+170
+00:06:20,000 --> 00:06:22,000
+Okay, what it simply means is
+
+171
+00:06:22,000 --> 00:06:24,000
+if you have an abstract method,
+
+172
+00:06:24,000 --> 00:06:27,000
+abstract method can belong to only abstract class.
+
+173
+00:06:27,000 --> 00:06:29,000
+So that means you have to make this class
+
+174
+00:06:29,000 --> 00:06:30,000
+as abstract as well.
+
+175
+00:06:30,000 --> 00:06:34,000
+So you can have abstract methods only in the abstract class
+
+176
+00:06:34,000 --> 00:06:38,000
+and whichever class is extending the abstract class
+
+177
+00:06:38,000 --> 00:06:39,000
+will have this drive method.
+
+178
+00:06:39,000 --> 00:06:41,000
+If we don't do that, it'll give you error.
+
+179
+00:06:41,000 --> 00:06:43,000
+Example, if I change the method name,
+
+180
+00:06:43,000 --> 00:06:44,000
+you can see it will give you error.
+
+181
+00:06:44,000 --> 00:06:47,000
+It says, the type WagonR must implement
+
+182
+00:06:47,000 --> 00:06:50,000
+the inherited abstract method Car.drive.
+
+183
+00:06:50,000 --> 00:06:53,000
+So if you are extending an abstract class,
+
+184
+00:06:53,000 --> 00:06:55,000
+you need to define it, compulsory,
+
+185
+00:06:55,000 --> 00:06:56,000
+otherwise, it will not work.
+
+186
+00:06:56,000 --> 00:06:57,000
+So you have to define,
+
+187
+00:06:57,000 --> 00:06:59,000
+you have to basically override the method.
+
+188
+00:06:59,000 --> 00:07:01,000
+Now, when someone creates an object of a car,
+
+189
+00:07:01,000 --> 00:07:04,000
+in fact, first of all, you can't create the object
+
+190
+00:07:04,000 --> 00:07:06,000
+of abstract class, very important point.
+
+191
+00:07:06,000 --> 00:07:08,000
+And that's why you can see we got a error here.
+
+192
+00:07:08,000 --> 00:07:11,000
+It says, cannot instantiate the type Car.
+
+193
+00:07:11,000 --> 00:07:14,000
+It simply means you cannot create object of car.
+
+194
+00:07:14,000 --> 00:07:16,000
+So the point, remember?
+
+195
+00:07:16,000 --> 00:07:18,000
+You cannot create object of an abstract class.
+
+196
+00:07:18,000 --> 00:07:21,000
+Okay, but then, can I create a reference of abstract class?
+
+197
+00:07:21,000 --> 00:07:22,000
+Yes, that is possible.
+
+198
+00:07:22,000 --> 00:07:26,000
+You can say Car obj, that is absolutely correct,
+
+199
+00:07:26,000 --> 00:07:27,000
+but if you want to create an object,
+
+200
+00:07:27,000 --> 00:07:31,000
+you have to create object of not car, but WagonR, okay?
+
+201
+00:07:31,000 --> 00:07:34,000
+And then with this obj, you can call drive,
+
+202
+00:07:34,000 --> 00:07:36,000
+we can call playMusic.
+
+203
+00:07:36,000 --> 00:07:38,000
+And we have talked about dynamic method dispatch.
+
+204
+00:07:38,000 --> 00:07:39,000
+And we know when you call drive,
+
+205
+00:07:39,000 --> 00:07:42,000
+it will be calling drive of WagonR, not of car.
+
+206
+00:07:42,000 --> 00:07:45,000
+Anyway, it is declared, right?
+
+207
+00:07:45,000 --> 00:07:47,000
+So basically, that's how you can create an abstract class.
+
+208
+00:07:47,000 --> 00:07:49,000
+That's how you can create an abstract method.
+
+209
+00:07:49,000 --> 00:07:51,000
+And basically, that's how you can restrict
+
+210
+00:07:51,000 --> 00:07:53,000
+the creation of the object here.
+
+211
+00:07:53,000 --> 00:07:54,000
+Now, a few more points to remember.
+
+212
+00:07:54,000 --> 00:07:57,000
+Is it compulsory to have an abstract method
+
+213
+00:07:57,000 --> 00:07:58,000
+in the abstract class?
+
+214
+00:07:58,000 --> 00:08:00,000
+I mean, we know that it is compulsory
+
+215
+00:08:00,000 --> 00:08:01,000
+to have the abstract method.
+
+216
+00:08:01,000 --> 00:08:03,000
+You need abstract class, right?
+
+217
+00:08:03,000 --> 00:08:05,000
+But is it compulsory to have
+
+218
+00:08:05,000 --> 00:08:06,000
+a abstract method in the abstract class?
+
+219
+00:08:06,000 --> 00:08:07,000
+Let's do that.
+
+220
+00:08:07,000 --> 00:08:10,000
+If you come in this section, okay?
+
+221
+00:08:10,000 --> 00:08:11,000
+You can see there's no problem.
+
+222
+00:08:11,000 --> 00:08:15,000
+It's not like a abstract class should have abstract method.
+
+223
+00:08:15,000 --> 00:08:17,000
+Abstract class can have abstract methods,
+
+224
+00:08:17,000 --> 00:08:19,000
+it can have normal methods.
+
+225
+00:08:19,000 --> 00:08:20,000
+So you can have an abstract class
+
+226
+00:08:20,000 --> 00:08:21,000
+with which only has abstract methods.
+
+227
+00:08:21,000 --> 00:08:23,000
+You can have abstract class
+
+228
+00:08:23,000 --> 00:08:27,000
+which has only implemented methods, which are this,
+
+229
+00:08:27,000 --> 00:08:29,000
+which are non-abstract methods.
+
+230
+00:08:29,000 --> 00:08:31,000
+And you can have a abstract class which can have both,
+
+231
+00:08:31,000 --> 00:08:34,000
+normal methods as well as the abstract method.
+
+232
+00:08:34,000 --> 00:08:36,000
+And you can create multiple abstract method, okay?
+
+233
+00:08:36,000 --> 00:08:38,000
+Example, if I can come back here
+
+234
+00:08:38,000 --> 00:08:41,000
+and say, hey, you know, I want a car to fly.
+
+235
+00:08:41,000 --> 00:08:44,000
+I dunno when this is possible,
+
+236
+00:08:44,000 --> 00:08:45,000
+but in the movies you see that, right?
+
+237
+00:08:45,000 --> 00:08:49,000
+So a car jumps from one building to other building, okay?
+
+238
+00:08:49,000 --> 00:08:50,000
+And I hope you know the movie name,
+
+239
+00:08:50,000 --> 00:08:53,000
+but anyway, so if you talk about this abstract method,
+
+240
+00:08:53,000 --> 00:08:55,000
+which is fly, and you can see I'm declaring it here.
+
+241
+00:08:55,000 --> 00:08:57,000
+Now, when you declare a method
+
+242
+00:08:57,000 --> 00:08:59,000
+and when you say you have an abstract class
+
+243
+00:08:59,000 --> 00:09:01,000
+which is getting implemented
+
+244
+00:09:01,000 --> 00:09:04,000
+or which is getting extended by another class,
+
+245
+00:09:04,000 --> 00:09:05,000
+it becomes compulsory for you
+
+246
+00:09:05,000 --> 00:09:07,000
+to define one more method here.
+
+247
+00:09:07,000 --> 00:09:09,000
+So you can say public, not abstract,
+
+248
+00:09:09,000 --> 00:09:11,000
+you can say public void.
+
+249
+00:09:11,000 --> 00:09:14,000
+You have to define fly as well, otherwise, it'll not work.
+
+250
+00:09:14,000 --> 00:09:17,000
+So you can say flying, okay?
+
+251
+00:09:17,000 --> 00:09:19,000
+And now, with this you can call the methods.
+
+252
+00:09:19,000 --> 00:09:24,000
+You can say obj.fly and this should work, compile, run.
+
+253
+00:09:25,000 --> 00:09:28,000
+And you can see it says Driving, play music, and Flying.
+
+254
+00:09:28,000 --> 00:09:30,000
+Now, there's one important thing here,
+
+255
+00:09:30,000 --> 00:09:33,000
+which is what if when you are creating
+
+256
+00:09:33,000 --> 00:09:35,000
+this class WagonR and then you are not able
+
+257
+00:09:35,000 --> 00:09:37,000
+to implement fly, what will happen?
+
+258
+00:09:37,000 --> 00:09:38,000
+First of all, it's compulsory
+
+259
+00:09:38,000 --> 00:09:40,000
+to define all the methods, okay?
+
+260
+00:09:40,000 --> 00:09:42,000
+All the abstract methods.
+
+261
+00:09:42,000 --> 00:09:45,000
+So you can see in this class, we have three methods,
+
+262
+00:09:45,000 --> 00:09:47,000
+but only two methods are abstract.
+
+263
+00:09:47,000 --> 00:09:48,000
+And that's why it says,
+
+264
+00:09:48,000 --> 00:09:50,000
+it should define fly as well as drive,
+
+265
+00:09:50,000 --> 00:09:51,000
+but we are not implementing fly.
+
+266
+00:09:51,000 --> 00:09:53,000
+So you can see it says, the type WagonR
+
+267
+00:09:53,000 --> 00:09:57,000
+must implement the inherited abstract method, Car.fly.
+
+268
+00:09:57,000 --> 00:09:59,000
+But what if you don't do that?
+
+269
+00:09:59,000 --> 00:10:02,000
+So in that case, if you have a class which is not able
+
+270
+00:10:02,000 --> 00:10:05,000
+to implement all the methods, in this case,
+
+271
+00:10:05,000 --> 00:10:07,000
+even this class becomes abstract class.
+
+272
+00:10:07,000 --> 00:10:09,000
+So you have to make it abstract class,
+
+273
+00:10:09,000 --> 00:10:11,000
+and you can see there's no error.
+
+274
+00:10:11,000 --> 00:10:14,000
+But the problem now is you can't create object
+
+275
+00:10:14,000 --> 00:10:15,000
+of abstract class, right?
+
+276
+00:10:15,000 --> 00:10:18,000
+So maybe you have to create a new class here by saying,
+
+277
+00:10:19,000 --> 00:10:24,000
+UpdatedWagonR which can also fly and this will extend.
+
+278
+00:10:24,000 --> 00:10:25,000
+Now, which class you want me to extend,
+
+279
+00:10:25,000 --> 00:10:27,000
+the car or the WagonR?
+
+280
+00:10:27,000 --> 00:10:28,000
+Of course, Wagoner, right?
+
+281
+00:10:28,000 --> 00:10:31,000
+Because you will get this dry feature from WagonR.
+
+282
+00:10:31,000 --> 00:10:34,000
+So you can simply extend it with WagonR.
+
+283
+00:10:34,000 --> 00:10:36,000
+And then here, in this class,
+
+284
+00:10:36,000 --> 00:10:38,000
+you can basically create object of fly.
+
+285
+00:10:38,000 --> 00:10:40,000
+In fact, if you are using IDE,
+
+286
+00:10:40,000 --> 00:10:41,000
+and if you don't, if you're lazy to type,
+
+287
+00:10:41,000 --> 00:10:45,000
+you can come to this error, and you can say Quick Fix,
+
+288
+00:10:45,000 --> 00:10:48,000
+add unimplemented methods, and it will do it for you.
+
+289
+00:10:48,000 --> 00:10:52,000
+Okay? And here, we can say Flying. So even you can do that.
+
+290
+00:10:52,000 --> 00:10:55,000
+The only thing is now the object will not be of WagonR.
+
+291
+00:10:55,000 --> 00:10:58,000
+The object will be of UpdatedWagonR.
+
+292
+00:10:59,000 --> 00:11:00,000
+Is it the method class name?
+
+293
+00:11:00,000 --> 00:11:03,000
+Okay, it should be updated, right?
+
+294
+00:11:03,000 --> 00:11:05,000
+So that's how you can create a object.
+
+295
+00:11:05,000 --> 00:11:07,000
+So again, we are not creating object of abstract class.
+
+296
+00:11:07,000 --> 00:11:09,000
+We are creating object of the class
+
+297
+00:11:09,000 --> 00:11:11,000
+which is not abstract.
+
+298
+00:11:11,000 --> 00:11:12,000
+Okay, now, since we are calling
+
+299
+00:11:12,000 --> 00:11:14,000
+this class as abstract class,
+
+300
+00:11:14,000 --> 00:11:15,000
+even this class should have a name, right?
+
+301
+00:11:15,000 --> 00:11:18,000
+So normally, we call them as a concrete class.
+
+302
+00:11:18,000 --> 00:11:22,000
+So we can say this is a concrete class.
+
+303
+00:11:22,000 --> 00:11:23,000
+Okay, so we have abstract class
+
+304
+00:11:23,000 --> 00:11:24,000
+and then we have concrete class.
+
+305
+00:11:24,000 --> 00:11:27,000
+So you can create object of a concrete class,
+
+306
+00:11:27,000 --> 00:11:29,000
+not an abstract class.
+
+307
+00:11:29,000 --> 00:11:32,000
+So I hope this makes sense. That's about abstract keyword.
+
+308
+00:11:32,000 --> 00:11:34,000
+So let me just reiterate.
+
+309
+00:11:34,000 --> 00:11:35,000
+Abstract keyword can be used
+
+310
+00:11:35,000 --> 00:11:37,000
+with methods if you want to declare them.
+
+311
+00:11:37,000 --> 00:11:39,000
+And if you have any abstract methods,
+
+312
+00:11:39,000 --> 00:11:41,000
+you have to make a class as abstract.
+
+313
+00:11:41,000 --> 00:11:43,000
+But again, on the other hand, if you have abstract class,
+
+314
+00:11:43,000 --> 00:11:46,000
+there's no compulsion that abstract class
+
+315
+00:11:46,000 --> 00:11:47,000
+should have abstract methods.
+
+316
+00:11:47,000 --> 00:11:50,000
+Abstract class can have normal methods also.
+
+317
+00:11:50,000 --> 00:11:51,000
+I mean, all these normal methods.
+
+318
+00:11:51,000 --> 00:11:54,000
+No abstract methods. Even that is possible.
+
+319
+00:11:54,000 --> 00:11:56,000
+Next point, remember, we cannot create object
+
+320
+00:11:56,000 --> 00:11:57,000
+of an abstract class.
+
+321
+00:11:57,000 --> 00:12:00,000
+If you want to create object, you have to get a class,
+
+322
+00:12:00,000 --> 00:12:02,000
+which implements all the methods,
+
+323
+00:12:02,000 --> 00:12:04,000
+a subclass which implements all the methods.
+
+324
+00:12:04,000 --> 00:12:06,000
+And then that class will be called as a concrete class,
+
+325
+00:12:06,000 --> 00:12:08,000
+and you can create object of it.
+
+326
+00:12:08,000 --> 00:12:09,000
+So that's about abstract keyword.
+
diff --git a/03 - Advance Java/006 Source-code.url b/03 - Advance Java/006 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/006 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/03 - Advance Java/007 Inner class_en.srt b/03 - Advance Java/007 Inner class_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..de7d610afb790f41250f908114ebd2678c75de0a
--- /dev/null
+++ b/03 - Advance Java/007 Inner class_en.srt	
@@ -0,0 +1,588 @@
+1
+00:00:03,000 --> 00:00:05,000
+-: In this video we'll talk about inner class.
+
+2
+00:00:05,000 --> 00:00:07,000
+That's right, a class inside a class.
+
+3
+00:00:07,000 --> 00:00:08,000
+I know that sounds weird at first,
+
+4
+00:00:08,000 --> 00:00:11,000
+but let me go with that.
+
+5
+00:00:11,000 --> 00:00:13,000
+See, most of the time when you build an application,
+
+6
+00:00:13,000 --> 00:00:16,000
+you might have a scenario where
+
+7
+00:00:16,000 --> 00:00:20,000
+a class will be used only for that particular purpose, okay?
+
+8
+00:00:20,000 --> 00:00:22,000
+So let's say you have a class A
+
+9
+00:00:22,000 --> 00:00:24,000
+and then that class needs variables
+
+10
+00:00:24,000 --> 00:00:25,000
+so we can do that.
+
+11
+00:00:25,000 --> 00:00:27,000
+Example, we have a class A here.
+
+12
+00:00:27,000 --> 00:00:28,000
+So when you have this class A,
+
+13
+00:00:28,000 --> 00:00:29,000
+this class can have variables,
+
+14
+00:00:29,000 --> 00:00:31,000
+this class can have methods, right?
+
+15
+00:00:31,000 --> 00:00:34,000
+Now, these variables and methods only work for this class A.
+
+16
+00:00:34,000 --> 00:00:36,000
+So if you want to access them,
+
+17
+00:00:36,000 --> 00:00:39,000
+you have to get A class first.
+
+18
+00:00:39,000 --> 00:00:40,000
+In the same way let's say if you have a class
+
+19
+00:00:40,000 --> 00:00:44,000
+where the class is totally dependent on class A,
+
+20
+00:00:44,000 --> 00:00:46,000
+there's no other need for it.
+
+21
+00:00:46,000 --> 00:00:50,000
+In that case, you can create a class inside the class, okay?
+
+22
+00:00:50,000 --> 00:00:52,000
+The way you do that is by defining a class like A,
+
+23
+00:00:52,000 --> 00:00:56,000
+and then you can define a class called B inside it.
+
+24
+00:00:56,000 --> 00:00:58,000
+Now, just the way you have class A here,
+
+25
+00:00:58,000 --> 00:01:00,000
+I can create variable that works,
+
+26
+00:01:00,000 --> 00:01:03,000
+we can say variable age,
+
+27
+00:01:03,000 --> 00:01:05,000
+and then we can have method as well,
+
+28
+00:01:05,000 --> 00:01:09,000
+which is public void show.
+
+29
+00:01:09,000 --> 00:01:10,000
+Now we have these two things,
+
+30
+00:01:10,000 --> 00:01:12,000
+we have a variable, which is age,
+
+31
+00:01:12,000 --> 00:01:13,000
+and then we have a method which is show,
+
+32
+00:01:13,000 --> 00:01:15,000
+and then we have a class as well.
+
+33
+00:01:15,000 --> 00:01:17,000
+So imagine a class having all three things,
+
+34
+00:01:17,000 --> 00:01:20,000
+a variable, a method, and a class.
+
+35
+00:01:20,000 --> 00:01:22,000
+And inside this class, let's say I create a method,
+
+36
+00:01:22,000 --> 00:01:24,000
+which is public void config.
+
+37
+00:01:24,000 --> 00:01:27,000
+And in this config, I will print something,
+
+38
+00:01:27,000 --> 00:01:29,000
+let's say in config,
+
+39
+00:01:29,000 --> 00:01:31,000
+just to print something, okay?
+
+40
+00:01:31,000 --> 00:01:34,000
+And I'm trying to make this example as simple as possible,
+
+41
+00:01:34,000 --> 00:01:35,000
+that's why I'm using this class name.
+
+42
+00:01:35,000 --> 00:01:36,000
+In real life, don't do that.
+
+43
+00:01:36,000 --> 00:01:39,000
+Make sure that you use proper class names.
+
+44
+00:01:39,000 --> 00:01:41,000
+And so let's say we have this scenario.
+
+45
+00:01:41,000 --> 00:01:44,000
+Now question is how will you call this config?
+
+46
+00:01:44,000 --> 00:01:45,000
+So it's very easy to call show.
+
+47
+00:01:45,000 --> 00:01:47,000
+In fact, I should print something here just to see
+
+48
+00:01:47,000 --> 00:01:51,000
+what it prints in show.
+
+49
+00:01:51,000 --> 00:01:53,000
+Now, question to you is how will you call this show?
+
+50
+00:01:53,000 --> 00:01:55,000
+And then we have seen this, right?
+
+51
+00:01:55,000 --> 00:01:58,000
+You simply have to create this object of A
+
+52
+00:01:58,000 --> 00:02:01,000
+and then you can call obj.show
+
+53
+00:02:03,000 --> 00:02:05,000
+I mean, show will perfectly work, right?
+
+54
+00:02:05,000 --> 00:02:08,000
+If I compile this code and run, you can see it says in show.
+
+55
+00:02:08,000 --> 00:02:11,000
+Now I want to call config.
+
+56
+00:02:11,000 --> 00:02:12,000
+How will you do that?
+
+57
+00:02:12,000 --> 00:02:14,000
+Of course, you will say if it is a class B,
+
+58
+00:02:14,000 --> 00:02:16,000
+then you have to get object of B to call this config.
+
+59
+00:02:16,000 --> 00:02:18,000
+Let's try.
+
+60
+00:02:18,000 --> 00:02:23,000
+If I try to create object of B by saying B obj1 new B,
+
+61
+00:02:24,000 --> 00:02:26,000
+you can see it'll give you an error.
+
+62
+00:02:26,000 --> 00:02:29,000
+It says B cannot be resolved.
+
+63
+00:02:29,000 --> 00:02:31,000
+Oh, it's not able to find B.
+
+64
+00:02:31,000 --> 00:02:34,000
+The thing is, B is not openly available, right?
+
+65
+00:02:34,000 --> 00:02:36,000
+B is a part of A.
+
+66
+00:02:36,000 --> 00:02:37,000
+So if you want to refer B here,
+
+67
+00:02:37,000 --> 00:02:39,000
+you need to say A.B.
+
+68
+00:02:39,000 --> 00:02:40,000
+So B belongs to A,
+
+69
+00:02:40,000 --> 00:02:42,000
+that's why you have to say this.
+
+70
+00:02:42,000 --> 00:02:44,000
+Okay, now while I'm doing this,
+
+71
+00:02:44,000 --> 00:02:46,000
+so when you say if you compile this code,
+
+72
+00:02:46,000 --> 00:02:48,000
+and if I go back here,
+
+73
+00:02:48,000 --> 00:02:49,000
+can you see that we got two classes
+
+74
+00:02:49,000 --> 00:02:50,000
+and we have seen this, right?
+
+75
+00:02:50,000 --> 00:02:52,000
+Every time you compile a code,
+
+76
+00:02:52,000 --> 00:02:55,000
+you will get those number of class files.
+
+77
+00:02:55,000 --> 00:02:56,000
+So you've got a classify for demo that makes sense.
+
+78
+00:02:56,000 --> 00:02:58,000
+You can see we have demo.class.
+
+79
+00:02:58,000 --> 00:03:03,000
+You will get A.class as well because A is a class,
+
+80
+00:03:03,000 --> 00:03:04,000
+but we also got,
+
+81
+00:03:04,000 --> 00:03:05,000
+B is also class, right?
+
+82
+00:03:05,000 --> 00:03:07,000
+It should have its own class file.
+
+83
+00:03:07,000 --> 00:03:08,000
+And that's right, we got it.
+
+84
+00:03:08,000 --> 00:03:10,000
+We got B.class.
+
+85
+00:03:10,000 --> 00:03:12,000
+The only thing is B belongs to A.
+
+86
+00:03:12,000 --> 00:03:15,000
+So the dollar symbol separates this two.
+
+87
+00:03:15,000 --> 00:03:17,000
+So it says B class belongs to B class
+
+88
+00:03:17,000 --> 00:03:20,000
+and that's why it's A dollar B.
+
+89
+00:03:20,000 --> 00:03:21,000
+Okay, that makes sense.
+
+90
+00:03:21,000 --> 00:03:25,000
+So if you want to access B, you have to say A.B.
+
+91
+00:03:25,000 --> 00:03:27,000
+That's how you access it and you can say obj1.
+
+92
+00:03:27,000 --> 00:03:30,000
+You can say there's no problem in declaring the variable.
+
+93
+00:03:30,000 --> 00:03:32,000
+The problem is when you say new,
+
+94
+00:03:32,000 --> 00:03:34,000
+now, how will you do it?
+
+95
+00:03:34,000 --> 00:03:36,000
+If you say B, it'll not work again.
+
+96
+00:03:36,000 --> 00:03:38,000
+It'll say cannot able to resolve B.
+
+97
+00:03:38,000 --> 00:03:41,000
+In that case, if you say A.B,
+
+98
+00:03:41,000 --> 00:03:43,000
+no, that's not the proper syntax.
+
+99
+00:03:43,000 --> 00:03:46,000
+The thing is, if you want to create object of B,
+
+100
+00:03:46,000 --> 00:03:49,000
+you need object of A first.
+
+101
+00:03:49,000 --> 00:03:50,000
+Now you will say why?
+
+102
+00:03:50,000 --> 00:03:51,000
+It's very simple.
+
+103
+00:03:51,000 --> 00:03:54,000
+If you want to call B, if you want to call this show,
+
+104
+00:03:54,000 --> 00:03:56,000
+now, show is a method, right?
+
+105
+00:03:56,000 --> 00:03:58,000
+It's a non-static method,
+
+106
+00:03:58,000 --> 00:04:02,000
+which means if you want to call show, you need object.
+
+107
+00:04:02,000 --> 00:04:05,000
+In the same way if you want to access this variable age,
+
+108
+00:04:05,000 --> 00:04:05,000
+you need object.
+
+109
+00:04:05,000 --> 00:04:09,000
+In the same way, if you want to create object of B,
+
+110
+00:04:09,000 --> 00:04:11,000
+you need object of A,
+
+111
+00:04:11,000 --> 00:04:14,000
+because that is a non non-static method.
+
+112
+00:04:14,000 --> 00:04:16,000
+Okay, so I'm focusing more on static here, right?
+
+113
+00:04:16,000 --> 00:04:18,000
+Can I create a static class?
+
+114
+00:04:18,000 --> 00:04:20,000
+Yes, we'll see that in some time,
+
+115
+00:04:20,000 --> 00:04:22,000
+but we got this object here.
+
+116
+00:04:22,000 --> 00:04:27,000
+And now using this obj1, I can call the config method.
+
+117
+00:04:27,000 --> 00:04:30,000
+If you want to create object of inner class,
+
+118
+00:04:30,000 --> 00:04:31,000
+which is be in this case,
+
+119
+00:04:31,000 --> 00:04:33,000
+you need to first specify where it belongs to.
+
+120
+00:04:33,000 --> 00:04:35,000
+So B belongs to A,
+
+121
+00:04:35,000 --> 00:04:37,000
+and then you need object of outer class,
+
+122
+00:04:37,000 --> 00:04:40,000
+which is obj here to create object of inner class.
+
+123
+00:04:40,000 --> 00:04:43,000
+And once you have that, you can simply call these methods
+
+124
+00:04:43,000 --> 00:04:44,000
+and that will properly work.
+
+125
+00:04:44,000 --> 00:04:47,000
+You can see what in show and in config.
+
+126
+00:04:47,000 --> 00:04:48,000
+Okay.
+
+127
+00:04:48,000 --> 00:04:50,000
+Now we have also focused on a static class, right?
+
+128
+00:04:50,000 --> 00:04:53,000
+You can also make this class as static.
+
+129
+00:04:53,000 --> 00:04:55,000
+And we all know when you refer it to a static class,
+
+130
+00:04:55,000 --> 00:04:57,000
+you don't need object.
+
+131
+00:04:57,000 --> 00:05:00,000
+So basically you don't call this with the help of object,
+
+132
+00:05:00,000 --> 00:05:02,000
+you can directly refer with A.B.
+
+133
+00:05:02,000 --> 00:05:05,000
+Now this will work only when the class is static,
+
+134
+00:05:05,000 --> 00:05:06,000
+the inner class is static.
+
+135
+00:05:06,000 --> 00:05:09,000
+It'll not work for non-static class.
+
+136
+00:05:09,000 --> 00:05:10,000
+Now can we really make static class?
+
+137
+00:05:10,000 --> 00:05:13,000
+Yes, we can, provided that it's an inner class.
+
+138
+00:05:13,000 --> 00:05:17,000
+If it is outer class, you can't make outer class static.
+
+139
+00:05:17,000 --> 00:05:18,000
+You can see, it'll give you error.
+
+140
+00:05:18,000 --> 00:05:21,000
+It says illegal modifier for a class A;
+
+141
+00:05:21,000 --> 00:05:25,000
+only public, abstract and final art permitted.
+
+142
+00:05:25,000 --> 00:05:27,000
+So basically you can't use static here.
+
+143
+00:05:27,000 --> 00:05:30,000
+Static can be used only for the inner class.
+
+144
+00:05:30,000 --> 00:05:33,000
+Okay, I hope that makes sense.
+
+145
+00:05:33,000 --> 00:05:34,000
+So that's a concept of inner class.
+
+146
+00:05:34,000 --> 00:05:36,000
+And in the upcoming videos,
+
+147
+00:05:36,000 --> 00:05:39,000
+we'll do something more within classes.
+
diff --git a/03 - Advance Java/007 Source-code.url b/03 - Advance Java/007 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/007 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/03 - Advance Java/008 Anonymous Inner class_en.srt b/03 - Advance Java/008 Anonymous Inner class_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..6ae0beaaf96b5653b2457257f5b997a92da1073f
--- /dev/null
+++ b/03 - Advance Java/008 Anonymous Inner class_en.srt	
@@ -0,0 +1,508 @@
+1
+00:00:00,000 --> 00:00:03,000
+(soft music plays)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: Now once we know about Inner Class,
+
+3
+00:00:05,000 --> 00:00:07,000
+let's talk about Anonymous Inner Class.
+
+4
+00:00:07,000 --> 00:00:10,000
+I know that sounds weird, right? Anonymous.
+
+5
+00:00:10,000 --> 00:00:12,000
+Anonymous simply means something which doesn't have a name.
+
+6
+00:00:12,000 --> 00:00:14,000
+Okay? So what I'll do is I will just try
+
+7
+00:00:14,000 --> 00:00:16,000
+to remove everything here
+
+8
+00:00:16,000 --> 00:00:19,000
+and let's work with this particular class, okay?
+
+9
+00:00:19,000 --> 00:00:21,000
+And in fact, I needed a A class,
+
+10
+00:00:21,000 --> 00:00:23,000
+let's say class A is there, okay?
+
+11
+00:00:23,000 --> 00:00:26,000
+And inside this class A, I'm creating a method,
+
+12
+00:00:26,000 --> 00:00:28,000
+which is public void show.
+
+13
+00:00:28,000 --> 00:00:31,000
+Again, just to keep it simple, I'm using simple names here
+
+14
+00:00:31,000 --> 00:00:34,000
+and here I will print in A show, okay?
+
+15
+00:00:34,000 --> 00:00:38,000
+And if I want to call A, of course, I will simply say A OBJ.
+
+16
+00:00:38,000 --> 00:00:40,000
+You need to create object of A.
+
+17
+00:00:40,000 --> 00:00:44,000
+And then I will say obj.show
+
+18
+00:00:44,000 --> 00:00:48,000
+Let's see if this works. Compile and run.
+
+19
+00:00:48,000 --> 00:00:48,000
+It works.
+
+20
+00:00:48,000 --> 00:00:51,000
+You can see got, in A Show, that perfectly works.
+
+21
+00:00:51,000 --> 00:00:53,000
+Now the question I have for you is very simple question:
+
+22
+00:00:53,000 --> 00:00:56,000
+What if I want to change the behavior of show method?
+
+23
+00:00:56,000 --> 00:00:58,000
+Okay, that means I wanted to do something else.
+
+24
+00:00:58,000 --> 00:01:01,000
+Now I know in your mind you have the idea, right?
+
+25
+00:01:01,000 --> 00:01:03,000
+We can simply create a class which is B,
+
+26
+00:01:03,000 --> 00:01:06,000
+and this class B will extend A.
+
+27
+00:01:06,000 --> 00:01:09,000
+So basically we're trying to do method over writing here.
+
+28
+00:01:09,000 --> 00:01:11,000
+In this B as well,
+
+29
+00:01:11,000 --> 00:01:13,000
+you will be having the same method, which is show,
+
+30
+00:01:13,000 --> 00:01:14,000
+which will print in B show.
+
+31
+00:01:14,000 --> 00:01:16,000
+We just want to do something else.
+
+32
+00:01:16,000 --> 00:01:18,000
+And by doing something else, what I mean by in this code,
+
+33
+00:01:18,000 --> 00:01:20,000
+I'm just trying to print something else,
+
+34
+00:01:20,000 --> 00:01:21,000
+but of course you can do it whatever you want.
+
+35
+00:01:21,000 --> 00:01:25,000
+I just want to change the behavior of this show method.
+
+36
+00:01:25,000 --> 00:01:27,000
+So we created a new class called B,
+
+37
+00:01:27,000 --> 00:01:31,000
+and here what we can do is we can create the object of B,
+
+38
+00:01:31,000 --> 00:01:33,000
+but the reference is of A.
+
+39
+00:01:33,000 --> 00:01:35,000
+So what we are doing is we are overriding
+
+40
+00:01:35,000 --> 00:01:37,000
+the behavior of show.
+
+41
+00:01:37,000 --> 00:01:39,000
+And then you will say, "Hey, we have
+
+42
+00:01:39,000 --> 00:01:40,000
+already talked about it," right?
+
+43
+00:01:40,000 --> 00:01:42,000
+We have talked about method of writing.
+
+44
+00:01:42,000 --> 00:01:43,000
+Hold on, hold your horses.
+
+45
+00:01:43,000 --> 00:01:46,000
+Let's see, if I compile this code and run,
+
+46
+00:01:46,000 --> 00:01:47,000
+it says, in B Show.
+
+47
+00:01:47,000 --> 00:01:50,000
+But now, if you think about this class, now first of all,
+
+48
+00:01:50,000 --> 00:01:53,000
+as we mentioned, every time you compile a code,
+
+49
+00:01:53,000 --> 00:01:55,000
+it'll create all the class files.
+
+50
+00:01:55,000 --> 00:01:59,000
+See, we got a B because of the previous code.
+
+51
+00:01:59,000 --> 00:02:01,000
+Let's delete that. You can see we got B.class as well.
+
+52
+00:02:01,000 --> 00:02:03,000
+Now you will say, what's the harm in that?
+
+53
+00:02:03,000 --> 00:02:08,000
+See the harm is, the only purpose of this Class B was
+
+54
+00:02:08,000 --> 00:02:12,000
+to extend or to extend a class to override the method.
+
+55
+00:02:12,000 --> 00:02:14,000
+And maybe it'll be used only once.
+
+56
+00:02:14,000 --> 00:02:17,000
+Now, of course, if it is using multiple times
+
+57
+00:02:17,000 --> 00:02:19,000
+in different places, of course
+
+58
+00:02:19,000 --> 00:02:22,000
+you should create a different class.
+
+59
+00:02:22,000 --> 00:02:25,000
+But what if we know that this class will be used only once,
+
+60
+00:02:25,000 --> 00:02:27,000
+only for this particular use?
+
+61
+00:02:27,000 --> 00:02:31,000
+In that scenario, why to create a new class?
+
+62
+00:02:31,000 --> 00:02:33,000
+Oh, then you will say, "If you don't get a new class,
+
+63
+00:02:33,000 --> 00:02:35,000
+how will you get a new implementation?"
+
+64
+00:02:35,000 --> 00:02:36,000
+Okay, let me show you something.
+
+65
+00:02:36,000 --> 00:02:40,000
+What if I can simply come back here just
+
+66
+00:02:40,000 --> 00:02:42,000
+before the semicolon
+
+67
+00:02:42,000 --> 00:02:45,000
+and I can define what should be the new implementation?
+
+68
+00:02:45,000 --> 00:02:48,000
+I know, this looks tricky, but just be with me.
+
+69
+00:02:48,000 --> 00:02:51,000
+So till this point, we have seen that first you have
+
+70
+00:02:51,000 --> 00:02:54,000
+to create a class and then you create the object, right?
+
+71
+00:02:54,000 --> 00:02:56,000
+And that's what we are doing from a long time.
+
+72
+00:02:56,000 --> 00:02:59,000
+But now this is the first time that I'm saying I want
+
+73
+00:02:59,000 --> 00:03:00,000
+to create object of A.
+
+74
+00:03:00,000 --> 00:03:05,000
+But this is the implementation, this is the design for it.
+
+75
+00:03:05,000 --> 00:03:07,000
+Don't go for the original design.
+
+76
+00:03:07,000 --> 00:03:08,000
+I will give you new design.
+
+77
+00:03:08,000 --> 00:03:11,000
+The new design is, I will use the same method name
+
+78
+00:03:11,000 --> 00:03:12,000
+or same method here.
+
+79
+00:03:12,000 --> 00:03:14,000
+The only change I want to do here is
+
+80
+00:03:14,000 --> 00:03:16,000
+it'll print in new show.
+
+81
+00:03:16,000 --> 00:03:20,000
+I'll just provide some invitation so that it'll look better.
+
+82
+00:03:20,000 --> 00:03:22,000
+So what I'm doing here is I'm providing a different
+
+83
+00:03:22,000 --> 00:03:26,000
+implementation for show method, okay?
+
+84
+00:03:26,000 --> 00:03:30,000
+And let's see if this works. I just want to see, compile.
+
+85
+00:03:30,000 --> 00:03:33,000
+And you can see that it says, in new show, it is not going
+
+86
+00:03:33,000 --> 00:03:34,000
+for the original method.
+
+87
+00:03:34,000 --> 00:03:37,000
+So we are providing a new implementation here.
+
+88
+00:03:37,000 --> 00:03:40,000
+Now, this is called Inner Class, okay?
+
+89
+00:03:40,000 --> 00:03:42,000
+You will say, "Hey, how it's a class?
+
+90
+00:03:42,000 --> 00:03:45,000
+We are not using a class keyword," right?
+
+91
+00:03:45,000 --> 00:03:46,000
+That's right, we are not using a class keyword
+
+92
+00:03:46,000 --> 00:03:48,000
+and we are not even giving a name to it.
+
+93
+00:03:48,000 --> 00:03:50,000
+And that's why it is a Inner Class,
+
+94
+00:03:50,000 --> 00:03:53,000
+because this class is created inside the demo class.
+
+95
+00:03:53,000 --> 00:03:56,000
+And also there's no name for the class.
+
+96
+00:03:56,000 --> 00:03:58,000
+And that's why if you go back to your files,
+
+97
+00:03:58,000 --> 00:04:01,000
+can you see this?
+
+98
+00:04:01,000 --> 00:04:04,000
+We got demo, inside that we have a class,
+
+99
+00:04:04,000 --> 00:04:06,000
+but there's no name for it.
+
+100
+00:04:06,000 --> 00:04:08,000
+And since we don't have a name for it, it says one,
+
+101
+00:04:08,000 --> 00:04:10,000
+of course, if you create multiple classes,
+
+102
+00:04:10,000 --> 00:04:12,000
+we'll have a different number.
+
+103
+00:04:12,000 --> 00:04:13,000
+It was a 2, 3, 4, and list goes on.
+
+104
+00:04:13,000 --> 00:04:16,000
+And since we don't have a name,
+
+105
+00:04:16,000 --> 00:04:17,000
+it is called anonymous class.
+
+106
+00:04:17,000 --> 00:04:21,000
+So this is anonymous in a class, which we are going
+
+107
+00:04:21,000 --> 00:04:22,000
+to use a lot in the upcoming videos.
+
+108
+00:04:22,000 --> 00:04:24,000
+Once we talk about interfaces,
+
+109
+00:04:24,000 --> 00:04:27,000
+once we talk about functional interfaces,
+
+110
+00:04:27,000 --> 00:04:28,000
+Lambda Expressions,
+
+111
+00:04:28,000 --> 00:04:30,000
+this is very famous concept, so just get used to it.
+
+112
+00:04:30,000 --> 00:04:32,000
+Now, if you want me
+
+113
+00:04:32,000 --> 00:04:34,000
+to type this code one second, I will do that for you.
+
+114
+00:04:34,000 --> 00:04:36,000
+What I will do is I will just go back here.
+
+115
+00:04:36,000 --> 00:04:40,000
+See, it is not difficult, it's just that you're unfamiliar
+
+116
+00:04:40,000 --> 00:04:42,000
+with this concept and it'll take some time.
+
+117
+00:04:42,000 --> 00:04:45,000
+Okay, so what you do is just before the semicolon and
+
+118
+00:04:45,000 --> 00:04:48,000
+after the constructor open the curly brackets and close,
+
+119
+00:04:48,000 --> 00:04:49,000
+this is your class.
+
+120
+00:04:49,000 --> 00:04:53,000
+And in this class you provide the method, which is show,
+
+121
+00:04:53,000 --> 00:04:56,000
+and whatever you wanna do in show, you can do that here,
+
+122
+00:04:56,000 --> 00:04:58,000
+you can say, I'm printing a new show.
+
+123
+00:04:58,000 --> 00:04:59,000
+And then you can call this show.
+
+124
+00:04:59,000 --> 00:05:01,000
+So when you call this show, it'll call the show
+
+125
+00:05:01,000 --> 00:05:04,000
+of the new implementation, not this one.
+
+126
+00:05:04,000 --> 00:05:07,000
+Okay? And yeah, that's how it works.
+
+127
+00:05:07,000 --> 00:05:11,000
+So that is your Anonymous Inner Class.
+
diff --git a/03 - Advance Java/008 Source-code.url b/03 - Advance Java/008 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/008 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/03 - Advance Java/009 Abstract and Anonymous Inner Class_en.srt b/03 - Advance Java/009 Abstract and Anonymous Inner Class_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..1b445eee518e45f55a66df9eaf59f64584c50a7b
--- /dev/null
+++ b/03 - Advance Java/009 Abstract and Anonymous Inner Class_en.srt	
@@ -0,0 +1,324 @@
+1
+00:00:00,000 --> 00:00:03,000
+(light calming music)
+
+2
+00:00:03,000 --> 00:00:05,000
+-: Okay, so we have talked about abstract class.
+
+3
+00:00:05,000 --> 00:00:07,000
+We have talked about inner class.
+
+4
+00:00:07,000 --> 00:00:09,000
+In fact, we have talked about anonymous inner class.
+
+5
+00:00:09,000 --> 00:00:12,000
+Can we just use both? Let's try.
+
+6
+00:00:12,000 --> 00:00:14,000
+What I will do is I will just make this class
+
+7
+00:00:14,000 --> 00:00:16,000
+as an abstract class
+
+8
+00:00:16,000 --> 00:00:18,000
+because I want to create this method show
+
+9
+00:00:18,000 --> 00:00:21,000
+as an abstract method.
+
+10
+00:00:21,000 --> 00:00:23,000
+Let's say this is abstract, okay?
+
+11
+00:00:23,000 --> 00:00:28,000
+And then let's say I'm not doing all those thing.
+
+12
+00:00:28,000 --> 00:00:29,000
+Now I have a question for you.
+
+13
+00:00:29,000 --> 00:00:31,000
+If I want to create a object
+
+14
+00:00:31,000 --> 00:00:34,000
+or if I want to instantiate A, can I do that?
+
+15
+00:00:34,000 --> 00:00:36,000
+Of course, in the abstract class we have seen,
+
+16
+00:00:36,000 --> 00:00:39,000
+we can't do that because you can't instantiate
+
+17
+00:00:39,000 --> 00:00:40,000
+the abstract class.
+
+18
+00:00:40,000 --> 00:00:43,000
+And we have found a solution as well.
+
+19
+00:00:43,000 --> 00:00:46,000
+You can create a separate class by saying extends A,
+
+20
+00:00:46,000 --> 00:00:48,000
+and then you can provide the implementation here,
+
+21
+00:00:48,000 --> 00:00:52,000
+you can just go here, quick fix, implement the method.
+
+22
+00:00:52,000 --> 00:00:54,000
+And one more thing, you might be saying
+
+23
+00:00:54,000 --> 00:00:56,000
+that I'm reviewing this line multiple times,
+
+24
+00:00:56,000 --> 00:00:57,000
+it's just that we have not talked about
+
+25
+00:00:57,000 --> 00:00:59,000
+what is @Override.
+
+26
+00:00:59,000 --> 00:01:00,000
+Well, we have a separate topic on that.
+
+27
+00:01:00,000 --> 00:01:03,000
+So at that point we'll discuss that.
+
+28
+00:01:03,000 --> 00:01:08,000
+So here, I just want to say in B Show, okay?
+
+29
+00:01:08,000 --> 00:01:11,000
+And then of course I can create the object of B
+
+30
+00:01:11,000 --> 00:01:15,000
+and that's done with the help of this object, obj,
+
+31
+00:01:15,000 --> 00:01:17,000
+can call show, again, we have seen this in
+
+32
+00:01:17,000 --> 00:01:19,000
+abstract class concept,
+
+33
+00:01:19,000 --> 00:01:21,000
+but I wanna talk about something else.
+
+34
+00:01:21,000 --> 00:01:23,000
+So you can see it says in B Show.
+
+35
+00:01:24,000 --> 00:01:27,000
+Now if you look at the entire purpose of this class B
+
+36
+00:01:27,000 --> 00:01:30,000
+is to implement the show method, that's it.
+
+37
+00:01:30,000 --> 00:01:34,000
+And if you are using this method only once,
+
+38
+00:01:34,000 --> 00:01:36,000
+then why to even create this class?
+
+39
+00:01:36,000 --> 00:01:37,000
+Can I use something else?
+
+40
+00:01:37,000 --> 00:01:41,000
+Can I use anonymous inner class here?
+
+41
+00:01:41,000 --> 00:01:43,000
+Okay, so what I'm saying is I can simply say
+
+42
+00:01:43,000 --> 00:01:47,000
+new A, and okay, it's not working,
+
+43
+00:01:47,000 --> 00:01:50,000
+but can I provide the implementation here?
+
+44
+00:01:50,000 --> 00:01:52,000
+And I can create a method which is public void.
+
+45
+00:01:52,000 --> 00:01:54,000
+In fact, I would just simply paste the code
+
+46
+00:01:54,000 --> 00:01:56,000
+because we already have that code with me.
+
+47
+00:01:56,000 --> 00:01:58,000
+And here I will say in new Show.
+
+48
+00:01:58,000 --> 00:02:01,000
+So what I'm doing is I'm providing the implementation
+
+49
+00:02:01,000 --> 00:02:05,000
+for the abstract class here itself, okay?
+
+50
+00:02:05,000 --> 00:02:06,000
+And you might be thinking,
+
+51
+00:02:06,000 --> 00:02:08,000
+we are still getting new A, right?
+
+52
+00:02:08,000 --> 00:02:11,000
+Is it the object of an abstract class?
+
+53
+00:02:11,000 --> 00:02:12,000
+We can't do that, right?
+
+54
+00:02:12,000 --> 00:02:14,000
+How we are doing this,
+
+55
+00:02:14,000 --> 00:02:16,000
+the thing is, this is a class here, right?
+
+56
+00:02:16,000 --> 00:02:17,000
+The anonymous in a class,
+
+57
+00:02:17,000 --> 00:02:21,000
+and we are creating the object of not A,
+
+58
+00:02:21,000 --> 00:02:25,000
+we are creating the object of this anonymous inner class.
+
+59
+00:02:25,000 --> 00:02:26,000
+That's a point to remember.
+
+60
+00:02:26,000 --> 00:02:28,000
+So most of the time when we have interfaces
+
+61
+00:02:28,000 --> 00:02:30,000
+or abstract class, we use this concept.
+
+62
+00:02:30,000 --> 00:02:33,000
+So if you want to implement the interface
+
+63
+00:02:33,000 --> 00:02:36,000
+or the abstract class only once,
+
+64
+00:02:36,000 --> 00:02:37,000
+then you can use anonymous in a class.
+
+65
+00:02:37,000 --> 00:02:39,000
+And this perfectly works.
+
+66
+00:02:39,000 --> 00:02:43,000
+So let me just try it out, compile this code and run.
+
+67
+00:02:43,000 --> 00:02:45,000
+You can see it works.
+
+68
+00:02:45,000 --> 00:02:46,000
+So we can use anonymous in a class
+
+69
+00:02:46,000 --> 00:02:49,000
+for the abstract class as well.
+
+70
+00:02:49,000 --> 00:02:52,000
+In fact, if you have multiple methods, you can still do it.
+
+71
+00:02:52,000 --> 00:02:54,000
+If let's say we have one more abstract method here,
+
+72
+00:02:54,000 --> 00:02:56,000
+which is public void, let's say config.
+
+73
+00:02:56,000 --> 00:02:59,000
+We can create a method for config as well.
+
+74
+00:02:59,000 --> 00:03:01,000
+And since we're using an IDE,
+
+75
+00:03:01,000 --> 00:03:04,000
+it give you the method so you can simply use this
+
+76
+00:03:04,000 --> 00:03:07,000
+and you can print in config.
+
+77
+00:03:07,000 --> 00:03:09,000
+So it's not just for one method.
+
+78
+00:03:09,000 --> 00:03:10,000
+If you have multiple methods,
+
+79
+00:03:10,000 --> 00:03:12,000
+you can provide the implementation
+
+80
+00:03:12,000 --> 00:03:15,000
+in the anonymous in a class.
+
+81
+00:03:15,000 --> 00:03:18,000
+So that's about abstract class and anonymous in the class.
+
diff --git a/03 - Advance Java/009 Source-code.url b/03 - Advance Java/009 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/009 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/03 - Advance Java/010 Source-code.url b/03 - Advance Java/010 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/010 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/03 - Advance Java/010 What is Interface_en.srt b/03 - Advance Java/010 What is Interface_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..6c456e35b872594494024253ca52dbf7d2f1fe2c
--- /dev/null
+++ b/03 - Advance Java/010 What is Interface_en.srt	
@@ -0,0 +1,792 @@
+1
+00:00:00,000 --> 00:00:03,000
+-: In this video, we'll talk about interfaces.
+
+2
+00:00:03,000 --> 00:00:05,000
+Now, before we start with interface,
+
+3
+00:00:05,000 --> 00:00:06,000
+let's talk about the abstract class.
+
+4
+00:00:06,000 --> 00:00:08,000
+Now, let's say I create abstract class here.
+
+5
+00:00:08,000 --> 00:00:11,000
+So we'll say abstract class A.
+
+6
+00:00:11,000 --> 00:00:14,000
+And in this class, let me create some methods.
+
+7
+00:00:14,000 --> 00:00:16,000
+Now, we all know in the abstract class,
+
+8
+00:00:16,000 --> 00:00:20,000
+we can create abstract methods and normal methods as well.
+
+9
+00:00:20,000 --> 00:00:21,000
+But let's say if I have abstract class,
+
+10
+00:00:21,000 --> 00:00:24,000
+which only has let's say abstract methods,
+
+11
+00:00:24,000 --> 00:00:28,000
+if I say public abstract void show,
+
+12
+00:00:28,000 --> 00:00:32,000
+and we have public abstract void config.
+
+13
+00:00:32,000 --> 00:00:33,000
+Now, when you have abstract class
+
+14
+00:00:33,000 --> 00:00:35,000
+with two abstract methods, of course this works.
+
+15
+00:00:35,000 --> 00:00:38,000
+There's no compulsion to have non-abstract methods here,
+
+16
+00:00:38,000 --> 00:00:40,000
+or we call them as concrete methods.
+
+17
+00:00:40,000 --> 00:00:41,000
+There's no need for them.
+
+18
+00:00:41,000 --> 00:00:43,000
+Now, when you have a situation
+
+19
+00:00:43,000 --> 00:00:45,000
+where you have abstract class,
+
+20
+00:00:45,000 --> 00:00:47,000
+which only has abstract methods,
+
+21
+00:00:47,000 --> 00:00:49,000
+we have another way of doing it.
+
+22
+00:00:49,000 --> 00:00:51,000
+Now see, all this are decided at design time.
+
+23
+00:00:51,000 --> 00:00:54,000
+So when you make an application at designing,
+
+24
+00:00:54,000 --> 00:00:56,000
+you specify things, okay?
+
+25
+00:00:56,000 --> 00:00:57,000
+What are the classes I need
+
+26
+00:00:57,000 --> 00:01:00,000
+and what are the abstract class we need?
+
+27
+00:01:00,000 --> 00:01:02,000
+So you create this hierarchy of system.
+
+28
+00:01:02,000 --> 00:01:04,000
+Of course we'll talk about that hierarchy in some time.
+
+29
+00:01:04,000 --> 00:01:07,000
+Why do we need it? But at this point, we create a hierarchy.
+
+30
+00:01:07,000 --> 00:01:10,000
+And when you have a class which only has abstract methods,
+
+31
+00:01:10,000 --> 00:01:13,000
+the other alternative for that is to create a interface.
+
+32
+00:01:13,000 --> 00:01:14,000
+So instead of creating an abstract class,
+
+33
+00:01:14,000 --> 00:01:17,000
+we can create an interface.
+
+34
+00:01:17,000 --> 00:01:19,000
+Most of the time we use this interface
+
+35
+00:01:19,000 --> 00:01:20,000
+in project development.
+
+36
+00:01:20,000 --> 00:01:23,000
+So let's understand that. So we have the interface A.
+
+37
+00:01:23,000 --> 00:01:25,000
+Now you will say, what is changing there?
+
+38
+00:01:25,000 --> 00:01:27,000
+Now, first of all, interface is not a class, okay?
+
+39
+00:01:27,000 --> 00:01:29,000
+So that's why that's the main difference
+
+40
+00:01:29,000 --> 00:01:31,000
+between abstract class and interface.
+
+41
+00:01:31,000 --> 00:01:32,000
+And by default,
+
+42
+00:01:32,000 --> 00:01:36,000
+every method in the interface is public abstract.
+
+43
+00:01:36,000 --> 00:01:38,000
+So these two keywords actually not required,
+
+44
+00:01:38,000 --> 00:01:40,000
+because anyway they are public abstract.
+
+45
+00:01:40,000 --> 00:01:41,000
+So even if you don't mention,
+
+46
+00:01:41,000 --> 00:01:44,000
+they are by default public abstract.
+
+47
+00:01:44,000 --> 00:01:45,000
+And that's why, if you can see,
+
+48
+00:01:45,000 --> 00:01:47,000
+when I put a semicolon just after the method,
+
+49
+00:01:47,000 --> 00:01:49,000
+there is no error,
+
+50
+00:01:49,000 --> 00:01:52,000
+because behind the scene, public abstract is there.
+
+51
+00:01:52,000 --> 00:01:54,000
+Now this is your interface.
+
+52
+00:01:54,000 --> 00:01:57,000
+So interface basically means it's like a class, just
+
+53
+00:01:57,000 --> 00:02:02,000
+that all the methods are by default, public abstract, okay?
+
+54
+00:02:02,000 --> 00:02:05,000
+But then how will I use this? How will I instantiate this?
+
+55
+00:02:05,000 --> 00:02:07,000
+The same problem was there with abstract class, right?
+
+56
+00:02:07,000 --> 00:02:09,000
+We cannot instantiate it.
+
+57
+00:02:09,000 --> 00:02:12,000
+Now, if you look at this, how do I instantiate? Let's try.
+
+58
+00:02:12,000 --> 00:02:14,000
+So I will say A obj.
+
+59
+00:02:14,000 --> 00:02:16,000
+See, there's no problem in creating a reference of it.
+
+60
+00:02:16,000 --> 00:02:20,000
+So that also means we are creating a type,
+
+61
+00:02:20,000 --> 00:02:21,000
+the way you create classes.
+
+62
+00:02:21,000 --> 00:02:24,000
+So let's say if A is a class, you can say A obj.
+
+63
+00:02:24,000 --> 00:02:25,000
+So A is a type, right?
+
+64
+00:02:25,000 --> 00:02:29,000
+In the same way here, the interface A is a type.
+
+65
+00:02:29,000 --> 00:02:30,000
+Okay, this works.
+
+66
+00:02:30,000 --> 00:02:34,000
+But now when you try to create object for this,
+
+67
+00:02:34,000 --> 00:02:35,000
+it will give you an error.
+
+68
+00:02:35,000 --> 00:02:37,000
+It says if you see the error,
+
+69
+00:02:37,000 --> 00:02:40,000
+it says "Cannot instantiate the type A,"
+
+70
+00:02:40,000 --> 00:02:43,000
+because it's interface, you can't instantiate it.
+
+71
+00:02:43,000 --> 00:02:45,000
+Okay, then what's the solution?
+
+72
+00:02:45,000 --> 00:02:47,000
+The solution is, see, first of all,
+
+73
+00:02:47,000 --> 00:02:48,000
+why do we create interface?
+
+74
+00:02:48,000 --> 00:02:50,000
+We create interface so that we can design something.
+
+75
+00:02:50,000 --> 00:02:51,000
+We can say, example, let's say
+
+76
+00:02:51,000 --> 00:02:55,000
+if you ask me about how do we create a table,
+
+77
+00:02:55,000 --> 00:02:58,000
+I can say, or maybe if you ask me how to reach somewhere,
+
+78
+00:02:58,000 --> 00:03:01,000
+so I can say, "Go straight, take a right, go straight,
+
+79
+00:03:01,000 --> 00:03:03,000
+take a right, take an auto, take a bus,
+
+80
+00:03:03,000 --> 00:03:05,000
+get down at the next stop."
+
+81
+00:03:05,000 --> 00:03:07,000
+So what I'm doing is I'm giving you the path, right?
+
+82
+00:03:07,000 --> 00:03:11,000
+I'm giving you design. You have to literally take a walk.
+
+83
+00:03:11,000 --> 00:03:14,000
+I will not walk for you. I will just show the directions.
+
+84
+00:03:14,000 --> 00:03:16,000
+In the same way, interface says,
+
+85
+00:03:16,000 --> 00:03:19,000
+"I will tell you what are the methods you need,
+
+86
+00:03:19,000 --> 00:03:21,000
+but I will not implement them.
+
+87
+00:03:21,000 --> 00:03:22,000
+It is your job to implement."
+
+88
+00:03:22,000 --> 00:03:25,000
+So when I say your, now I'm talking about classes.
+
+89
+00:03:25,000 --> 00:03:28,000
+See, ultimately you create object of a class,
+
+90
+00:03:28,000 --> 00:03:31,000
+interface just show you the design.
+
+91
+00:03:31,000 --> 00:03:33,000
+So here, what I can do is I can create a class,
+
+92
+00:03:33,000 --> 00:03:34,000
+let's say class B.
+
+93
+00:03:34,000 --> 00:03:36,000
+So we have a class B here.
+
+94
+00:03:36,000 --> 00:03:37,000
+And then in this class,
+
+95
+00:03:37,000 --> 00:03:40,000
+I want to implement these two methods.
+
+96
+00:03:40,000 --> 00:03:43,000
+Now, in terms of abstract class, we say extends, right?
+
+97
+00:03:43,000 --> 00:03:46,000
+Because class extends another class.
+
+98
+00:03:46,000 --> 00:03:48,000
+Here A is the interface.
+
+99
+00:03:48,000 --> 00:03:50,000
+We have to use a different keyword here.
+
+100
+00:03:50,000 --> 00:03:52,000
+The keyword which we use is implements.
+
+101
+00:03:52,000 --> 00:03:54,000
+So whenever you want to implement the interface,
+
+102
+00:03:54,000 --> 00:03:57,000
+you say implements keyword.
+
+103
+00:03:57,000 --> 00:04:00,000
+And when you say implements, it becomes compulsory for you
+
+104
+00:04:00,000 --> 00:04:02,000
+to define both the methods, okay?
+
+105
+00:04:02,000 --> 00:04:04,000
+If you fail to define both the methods,
+
+106
+00:04:04,000 --> 00:04:08,000
+by default, your class also becomes abstract, okay?
+
+107
+00:04:08,000 --> 00:04:10,000
+But we don't want to create abstract class, right?
+
+108
+00:04:10,000 --> 00:04:11,000
+We want to create a concrete class.
+
+109
+00:04:11,000 --> 00:04:13,000
+We want to create object of B.
+
+110
+00:04:13,000 --> 00:04:18,000
+In that case, it's your job to define both the methods.
+
+111
+00:04:18,000 --> 00:04:20,000
+Okay, there's one way you can use a shortcut here.
+
+112
+00:04:20,000 --> 00:04:22,000
+You can just go back here and say Quick Fix.
+
+113
+00:04:22,000 --> 00:04:24,000
+It will ask you to implement the methods,
+
+114
+00:04:24,000 --> 00:04:26,000
+or you can do the hard work.
+
+115
+00:04:26,000 --> 00:04:28,000
+You can say public void show.
+
+116
+00:04:28,000 --> 00:04:30,000
+And then you can define something here.
+
+117
+00:04:30,000 --> 00:04:33,000
+I can say I'm defining in show.
+
+118
+00:04:33,000 --> 00:04:35,000
+And then we can define another method as well,
+
+119
+00:04:35,000 --> 00:04:38,000
+which is config or public void config.
+
+120
+00:04:38,000 --> 00:04:42,000
+And here we can define in config.
+
+121
+00:04:42,000 --> 00:04:43,000
+So basically what you're doing is
+
+122
+00:04:43,000 --> 00:04:46,000
+you are implementing both the methods.
+
+123
+00:04:46,000 --> 00:04:47,000
+As I mentioned before,
+
+124
+00:04:47,000 --> 00:04:49,000
+if you fail to implement these methods,
+
+125
+00:04:49,000 --> 00:04:51,000
+this class becomes an abstract class,
+
+126
+00:04:51,000 --> 00:04:53,000
+but we are implementing it, right?
+
+127
+00:04:53,000 --> 00:04:54,000
+Now, when you implement,
+
+128
+00:04:54,000 --> 00:04:57,000
+basically you can't create object of A,
+
+129
+00:04:57,000 --> 00:05:02,000
+but you can create object of B, and you can see it works.
+
+130
+00:05:02,000 --> 00:05:06,000
+And now using this obj I can call show.
+
+131
+00:05:06,000 --> 00:05:10,000
+I can call, what other method we have? We have config.
+
+132
+00:05:10,000 --> 00:05:12,000
+So we can call both the methods and that perfectly works.
+
+133
+00:05:12,000 --> 00:05:14,000
+If I compile and run this code,
+
+134
+00:05:14,000 --> 00:05:17,000
+you can see it says, "in show," "in config."
+
+135
+00:05:17,000 --> 00:05:20,000
+Okay, what else? Can I have?
+
+136
+00:05:20,000 --> 00:05:23,000
+So the way you create variables here,
+
+137
+00:05:23,000 --> 00:05:24,000
+so the way you create methods here,
+
+138
+00:05:24,000 --> 00:05:26,000
+can I create variables?
+
+139
+00:05:26,000 --> 00:05:28,000
+Now, first of all, we don't define variables, right?
+
+140
+00:05:28,000 --> 00:05:30,000
+We declare them. So we can actually.
+
+141
+00:05:30,000 --> 00:05:34,000
+So if I say int, let's say age, that's a variable. I know.
+
+142
+00:05:34,000 --> 00:05:36,000
+I don't know why I'm taking this age variable every time,
+
+143
+00:05:36,000 --> 00:05:38,000
+but let's say we have int age here,
+
+144
+00:05:38,000 --> 00:05:43,000
+and let's say we have string area, so that's a area name,
+
+145
+00:05:43,000 --> 00:05:45,000
+but you can see we got an error.
+
+146
+00:05:45,000 --> 00:05:48,000
+That means I cannot create variables. That's weird.
+
+147
+00:05:48,000 --> 00:05:50,000
+I just said we can, right?
+
+148
+00:05:50,000 --> 00:05:53,000
+See, the only thing is every variable in the interface,
+
+149
+00:05:53,000 --> 00:05:55,000
+we can create actually those variables.
+
+150
+00:05:55,000 --> 00:06:00,000
+The only thing is they are by default, final and static.
+
+151
+00:06:00,000 --> 00:06:03,000
+So all the variables inside the interface are by default,
+
+152
+00:06:03,000 --> 00:06:07,000
+final and static, okay?
+
+153
+00:06:07,000 --> 00:06:10,000
+So that means we have to first initialize the variable.
+
+154
+00:06:10,000 --> 00:06:11,000
+So when you say it's final,
+
+155
+00:06:11,000 --> 00:06:13,000
+we have to initialize the variable, right?
+
+156
+00:06:13,000 --> 00:06:15,000
+Okay, that's not my age, but let's say 44,
+
+157
+00:06:15,000 --> 00:06:18,000
+and let's say area is Mumbai, okay?
+
+158
+00:06:18,000 --> 00:06:20,000
+So basically what we're defining is
+
+159
+00:06:20,000 --> 00:06:21,000
+we are defining the age, which is 44,
+
+160
+00:06:21,000 --> 00:06:23,000
+and the area is Mumbai.
+
+161
+00:06:23,000 --> 00:06:28,000
+Now these variables are final and static.
+
+162
+00:06:28,000 --> 00:06:30,000
+Now, first of all, since they are static,
+
+163
+00:06:30,000 --> 00:06:33,000
+which means we can directly use the interface name.
+
+164
+00:06:33,000 --> 00:06:34,000
+Remember when we use static variable,
+
+165
+00:06:34,000 --> 00:06:38,000
+we don't have to use the object.
+
+166
+00:06:38,000 --> 00:06:38,000
+Example, if I want
+
+167
+00:06:38,000 --> 00:06:41,000
+to print the value of name or area here,
+
+168
+00:06:41,000 --> 00:06:46,000
+I can simply say A., A is the interface, A.area.
+
+169
+00:06:47,000 --> 00:06:49,000
+I can directly use it, not with the object.
+
+170
+00:06:50,000 --> 00:06:51,000
+And if I compile and run, it works.
+
+171
+00:06:51,000 --> 00:06:53,000
+You can say we got Mumbai.
+
+172
+00:06:53,000 --> 00:06:56,000
+If I try to change the value of this,
+
+173
+00:06:56,000 --> 00:07:00,000
+if I say A.area is equal to, let's say if I want
+
+174
+00:07:00,000 --> 00:07:05,000
+to change the area to Hyderabad, it's not working.
+
+175
+00:07:05,000 --> 00:07:08,000
+You can see it says "The final field," that's right.
+
+176
+00:07:08,000 --> 00:07:11,000
+The area is final, it is static.
+
+177
+00:07:11,000 --> 00:07:13,000
+We are using directly the interface name
+
+178
+00:07:13,000 --> 00:07:15,000
+and it's also final, okay?
+
+179
+00:07:15,000 --> 00:07:17,000
+So that's one thing you have to remember.
+
+180
+00:07:17,000 --> 00:07:20,000
+Now, you might be thinking why it has to be static final.
+
+181
+00:07:20,000 --> 00:07:22,000
+See, first of all,
+
+182
+00:07:22,000 --> 00:07:24,000
+you don't instantiate the interface, right?
+
+183
+00:07:24,000 --> 00:07:26,000
+Whatever you instantiate is a class
+
+184
+00:07:26,000 --> 00:07:29,000
+and you're not doing extends, you're doing implements.
+
+185
+00:07:29,000 --> 00:07:33,000
+What you get in implements is only the methods, right?
+
+186
+00:07:33,000 --> 00:07:35,000
+You don't get the variables there in implements.
+
+187
+00:07:35,000 --> 00:07:37,000
+So that's why it is static,
+
+188
+00:07:37,000 --> 00:07:39,000
+because we want to use the interface name,
+
+189
+00:07:39,000 --> 00:07:42,000
+and final, because interface objects
+
+190
+00:07:42,000 --> 00:07:46,000
+or interface don't have their own memory in the heap, right?
+
+191
+00:07:46,000 --> 00:07:49,000
+What you create object of is of B, not of A.
+
+192
+00:07:50,000 --> 00:07:52,000
+So if you don't have your own memory,
+
+193
+00:07:52,000 --> 00:07:54,000
+how can you have a non final variable?
+
+194
+00:07:54,000 --> 00:07:56,000
+So this is interface.
+
+195
+00:07:56,000 --> 00:07:57,000
+Now, in the next video,
+
+196
+00:07:57,000 --> 00:07:59,000
+let's try to understand why do we need interface
+
+197
+00:07:59,000 --> 00:08:00,000
+and why do we even need abstract class?
+
+198
+00:08:00,000 --> 00:08:02,000
+Okay, let's talk about those things in the next video.
+
diff --git a/03 - Advance Java/011 More on Interfaces_en.srt b/03 - Advance Java/011 More on Interfaces_en.srt
new file mode 100644
index 0000000000000000000000000000000000000000..af94a39f659e70958527916acf3d9ccd30393735
--- /dev/null
+++ b/03 - Advance Java/011 More on Interfaces_en.srt	
@@ -0,0 +1,312 @@
+1
+00:00:00,000 --> 00:00:02,000
+-: In fact, before talking about the need for interface,
+
+2
+00:00:02,000 --> 00:00:04,000
+we have one more thing to add here.
+
+3
+00:00:04,000 --> 00:00:08,000
+So let's say if I have a interface and I'm creating a class
+
+4
+00:00:08,000 --> 00:00:10,000
+which implements A, one interface here,
+
+5
+00:00:10,000 --> 00:00:13,000
+can a class implement multiple interface?
+
+6
+00:00:13,000 --> 00:00:16,000
+Example, let's say if I have interface, which is called X.
+
+7
+00:00:16,000 --> 00:00:21,000
+So if I say interface X, so B class implements A and X both.
+
+8
+00:00:22,000 --> 00:00:23,000
+And the answer is yes.
+
+9
+00:00:23,000 --> 00:00:24,000
+If you can see, there's no error here.
+
+10
+00:00:24,000 --> 00:00:26,000
+The only thing is whatever method you define here,
+
+11
+00:00:26,000 --> 00:00:29,000
+so let's say the method name here is run.
+
+12
+00:00:29,000 --> 00:00:31,000
+You can see we got an error here.
+
+13
+00:00:31,000 --> 00:00:32,000
+The only thing you have to do is
+
+14
+00:00:32,000 --> 00:00:34,000
+you have to define run as well.
+
+15
+00:00:34,000 --> 00:00:37,000
+So you will say public void run.
+
+16
+00:00:37,000 --> 00:00:39,000
+So basically we can have one class
+
+17
+00:00:39,000 --> 00:00:41,000
+implementing multiple interfaces.
+
+18
+00:00:41,000 --> 00:00:43,000
+Now that's not the case with abstract class, right?
+
+19
+00:00:43,000 --> 00:00:46,000
+Because in abstract class, we can extend only one class.
+
+20
+00:00:46,000 --> 00:00:47,000
+In interface,
+
+21
+00:00:47,000 --> 00:00:51,000
+you can have a class implementing multiple interfaces.
+
+22
+00:00:51,000 --> 00:00:56,000
+So here I can simply print running, okay?
+
+23
+00:00:56,000 --> 00:00:58,000
+So what we are doing is we are using multiple methods here.
+
+24
+00:00:58,000 --> 00:01:00,000
+We have three methods coming from two different interfaces.
+
+25
+00:01:00,000 --> 00:01:03,000
+This interface says two methods, show and config.
+
+26
+00:01:03,000 --> 00:01:07,000
+And this interface is, has only one method, which is run.
+
+27
+00:01:07,000 --> 00:01:10,000
+And you can see we got three methods here.
+
+28
+00:01:10,000 --> 00:01:10,000
+There's one more thing.
+
+29
+00:01:10,000 --> 00:01:12,000
+Let's say we have one more interface,
+
+30
+00:01:12,000 --> 00:01:15,000
+which is called interface Y.
+
+31
+00:01:15,000 --> 00:01:17,000
+Now the thing is when you talk about class and class,
+
+32
+00:01:17,000 --> 00:01:19,000
+a class can extend another class, right?
+
+33
+00:01:19,000 --> 00:01:23,000
+What about interface? But can we do interface and interface?
+
+34
+00:01:23,000 --> 00:01:25,000
+What keyword we have to use here?
+
+35
+00:01:25,000 --> 00:01:27,000
+See, whenever you have interface to interface,
+
+36
+00:01:27,000 --> 00:01:28,000
+we say extends.
+
+37
+00:01:28,000 --> 00:01:31,000
+So interface Y extends X.
+
+38
+00:01:31,000 --> 00:01:34,000
+So inheritance is valid here as well.
+
+39
+00:01:34,000 --> 00:01:36,000
+Now in this Y interface,
+
+40
+00:01:36,000 --> 00:01:38,000
+you'll be having a method called run.
+
+41
+00:01:38,000 --> 00:01:40,000
+So that's the inheritance, okay?
+
+42
+00:01:40,000 --> 00:01:44,000
+So you will get this declaration in the interface Y as well.
+
+43
+00:01:44,000 --> 00:01:45,000
+Let me show you.
+
+44
+00:01:45,000 --> 00:01:48,000
+If I remove this X and if I keep Y,
+
+45
+00:01:48,000 --> 00:01:49,000
+even now we have to use run.
+
+46
+00:01:49,000 --> 00:01:51,000
+Otherwise, if you remove run from here,
+
+47
+00:01:51,000 --> 00:01:54,000
+if you come in this part, you can see, it'll give you error.
+
+48
+00:01:54,000 --> 00:01:57,000
+It says "The type B must
+
+49
+00:01:57,000 --> 00:02:01,000
+implement the inherited abstract method run," okay?
+
+50
+00:02:01,000 --> 00:02:03,000
+But we are implementing Y, right?
+
+51
+00:02:03,000 --> 00:02:08,000
+It's just that Y extends X, so we have to use run.
+
+52
+00:02:08,000 --> 00:02:09,000
+Now point to remember here is
+
+53
+00:02:09,000 --> 00:02:14,000
+whenever you have a class to class, we say they extends.
+
+54
+00:02:15,000 --> 00:02:17,000
+Whenever you have class to interface,
+
+55
+00:02:17,000 --> 00:02:20,000
+basically a class is implementing interface,
+
+56
+00:02:20,000 --> 00:02:22,000
+so we have to say implements.
+
+57
+00:02:22,000 --> 00:02:25,000
+And whenever you have interface to interface,
+
+58
+00:02:25,000 --> 00:02:28,000
+we say that extends again.
+
+59
+00:02:28,000 --> 00:02:30,000
+Okay, so this is the point you have to remember.
+
+60
+00:02:30,000 --> 00:02:33,000
+So again, I will uncomment this part, okay?
+
+61
+00:02:33,000 --> 00:02:35,000
+Now there's only one thing you have to remember.
+
+62
+00:02:35,000 --> 00:02:38,000
+Whenever you create a reference of A interface
+
+63
+00:02:38,000 --> 00:02:40,000
+and object of B, which is a class,
+
+64
+00:02:40,000 --> 00:02:43,000
+I can only call two methods, which is of part A.
+
+65
+00:02:43,000 --> 00:02:46,000
+If I try to call run with A, it will not work,
+
+66
+00:02:46,000 --> 00:02:50,000
+because A has no idea what run method is.
+
+67
+00:02:50,000 --> 00:02:53,000
+If you can see in A, we don't have run.
+
+68
+00:02:53,000 --> 00:02:54,000
+In fact, what I will do is
+
+69
+00:02:54,000 --> 00:02:57,000
+I will just remove this code for time being, yeah.
+
+70
+00:02:57,000 --> 00:02:59,000
+And then if you want to implement run,
+
+71
+00:02:59,000 --> 00:03:01,000
+if you want to call run, in that case,
+
+72
+00:03:01,000 --> 00:03:04,000
+we need to create the reference of X,
+
+73
+00:03:04,000 --> 00:03:07,000
+which is obj1 is equal to new B.
+
+74
+00:03:07,000 --> 00:03:10,000
+Now, with this obj1, I can call run,
+
+75
+00:03:10,000 --> 00:03:13,000
+but again, I can't call two other methods, okay?
+
+76
+00:03:13,000 --> 00:03:15,000
+So that's one thing you have to remember.
+
+77
+00:03:15,000 --> 00:03:18,000
+Okay now, once we are good with this, let's try
+
+78
+00:03:18,000 --> 00:03:21,000
+to understand what's the need of the interface.
+
diff --git a/03 - Advance Java/011 Source-code.url b/03 - Advance Java/011 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/011 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/03 - Advance Java/012 Source-code.url b/03 - Advance Java/012 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/012 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file
diff --git a/03 - Advance Java/013 Source-code.url b/03 - Advance Java/013 Source-code.url
new file mode 100644
index 0000000000000000000000000000000000000000..f77c52ec3a0c9fa0c49360cf16ad3a6e212fb948
--- /dev/null
+++ b/03 - Advance Java/013 Source-code.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://github.com/navinreddy20/Javacode.git
\ No newline at end of file