19 - Java Collections Framework/002 Collection Interface_en.srt

1
00:00:06,000 --> 00:00:06,000
Hello.

2
00:00:06,000 --> 00:00:09,000
Students, in this lesson, we are going to learn what connections are.

3
00:00:10,000 --> 00:00:15,000
This is very important topic because connection interface is implemented by all connections implementations

4
00:00:15,000 --> 00:00:16,000
in Java.

5
00:00:16,000 --> 00:00:23,000
That's why understanding of collection interface is a key for understanding of all other collections

6
00:00:23,000 --> 00:00:23,000
in Java.

7
00:00:24,000 --> 00:00:28,000
So today our primary focus is learning of collection interface.

8
00:00:28,000 --> 00:00:35,000
I'm going to show you your middle class diagram, will understand what it is and how we can use it in

9
00:00:35,000 --> 00:00:36,000
the future.

10
00:00:36,000 --> 00:00:42,000
To understand a type structure during the lesson will understand what methods collection interface has

11
00:00:42,000 --> 00:00:43,000
and why do we need them.

12
00:00:44,000 --> 00:00:50,000
We will review abstract and default methods of collection interface and at the end of the lesson, we'll

13
00:00:50,000 --> 00:00:52,000
look at the collection source code.

14
00:00:52,000 --> 00:00:53,000
Let's start.

15
00:00:53,000 --> 00:00:59,000
I suggest that our lesson from this slide on this slide, you may see visualization of what the collection

16
00:00:59,000 --> 00:01:02,000
is to understand collection.

17
00:01:02,000 --> 00:01:07,000
Imagine the back, the big back where you may put all your stuff.

18
00:01:07,000 --> 00:01:15,000
You might put your product, user card and all other objects, and you can retrieve exactly user or

19
00:01:15,000 --> 00:01:19,000
product or cards by its index like you did in array.

20
00:01:20,000 --> 00:01:25,000
What you can do is to put all things from your back on the floor and go over them one by one.

21
00:01:26,000 --> 00:01:31,000
We're also going to learn in the separate lessons, the specific type that is developed to go over each

22
00:01:31,000 --> 00:01:32,000
element.

23
00:01:32,000 --> 00:01:34,000
What else we can do with these?

24
00:01:34,000 --> 00:01:40,000
Back to answer this question, let's take a look at collection interface and we'll learn what else we

25
00:01:40,000 --> 00:01:42,000
can do with our bag of elements.

26
00:01:43,000 --> 00:01:49,000
Here is a class diagram we are going to learn with your UML language that is unified model and language

27
00:01:49,000 --> 00:01:50,000
in detail a bit later.

28
00:01:51,000 --> 00:01:54,000
But this is what is used to call class diagram.

29
00:01:54,000 --> 00:01:59,000
And while being a software engineer, you are going to see such diagrams very often.

30
00:02:00,000 --> 00:02:01,000
What do we have here?

31
00:02:01,000 --> 00:02:06,000
We can see that collection interface extends a terrible interface, a terrible interface.

32
00:02:06,000 --> 00:02:10,000
We are going to learn in a separate lesson, the same as Iterator.

33
00:02:10,000 --> 00:02:17,000
But in short, this is an interface that stands on top of all collections interfaces to make sure that

34
00:02:17,000 --> 00:02:23,000
it will be possible to iterate over each element in each implementation of collection interface.

35
00:02:24,000 --> 00:02:29,000
Today we are going to focus on collection interface and we will start learning it from this class diagram.

36
00:02:30,000 --> 00:02:32,000
Let me give you a quick introduction regarding symbols here.

37
00:02:33,000 --> 00:02:40,000
You can find indication whether this type interface or no, that is our interface text right above the

38
00:02:40,000 --> 00:02:41,000
interface name.

39
00:02:41,000 --> 00:02:46,000
We can see that it's Arabel and collections, both interfaces here.

40
00:02:46,000 --> 00:02:52,000
We can see list of methods that each specific type has, plus some means that this method is public.

41
00:02:53,000 --> 00:02:55,000
After that goes method signature.

42
00:02:55,000 --> 00:02:59,000
That is method, name and method parameters followed by colon.

43
00:02:59,000 --> 00:03:03,000
And we can find return type right after the column.

44
00:03:03,000 --> 00:03:09,000
For example, the first method in the list in collection interface is this method without parameters

45
00:03:09,000 --> 00:03:11,000
that returns in value.

46
00:03:11,000 --> 00:03:12,000
Does it make sense now?

47
00:03:13,000 --> 00:03:18,000
This knowledge will help you to understand class diagrams written down on human language.

48
00:03:19,000 --> 00:03:21,000
And let's answer our original question.

49
00:03:21,000 --> 00:03:23,000
What else we can do with this back?

50
00:03:24,000 --> 00:03:26,000
We can check a number of elements in it.

51
00:03:26,000 --> 00:03:28,000
That is what size method does.

52
00:03:28,000 --> 00:03:31,000
We can check if this bag is empty or no.

53
00:03:31,000 --> 00:03:34,000
We can check if this bag is empty or no.

54
00:03:34,000 --> 00:03:41,000
That's why when it is empty, we can ask our back elements, does it contain some specific element or

55
00:03:41,000 --> 00:03:45,000
no contains measures that will help us with this task.

56
00:03:45,000 --> 00:03:51,000
We have also matters that control collection of elements, interior objects and methods that can turn

57
00:03:51,000 --> 00:03:54,000
collection of elements into the array of specific types.

58
00:03:54,000 --> 00:04:00,000
For example, if your collection contains only elements of product type, we can convert our collection

59
00:04:00,000 --> 00:04:04,000
into of product elements, but not in the array of objects.

60
00:04:04,000 --> 00:04:07,000
If you don't want, can you feel the difference?

61
00:04:08,000 --> 00:04:08,000
After that?

62
00:04:08,000 --> 00:04:11,000
We can see methods that we already kind of discuss.

63
00:04:11,000 --> 00:04:12,000
Let us add methods.

64
00:04:13,000 --> 00:04:15,000
I can add elements to the collection.

65
00:04:15,000 --> 00:04:21,000
I can also remove elements from the collection and to remove elements from the collection, I have to

66
00:04:21,000 --> 00:04:23,000
pass this exact element.

67
00:04:24,000 --> 00:04:30,000
Another important behavior, we can check whether this collection contains all elements that other collection

68
00:04:30,000 --> 00:04:30,000
has.

69
00:04:30,000 --> 00:04:32,000
That is our contains all method.

70
00:04:33,000 --> 00:04:36,000
We can add all elements from one collection to another.

71
00:04:36,000 --> 00:04:43,000
To do this, we have to use at all method and we can remove all elements from the current collections

72
00:04:43,000 --> 00:04:50,000
and other collection has that is our remove all method and believe you can see on the slide that message

73
00:04:50,000 --> 00:04:51,000
that we have just discussed.

74
00:04:51,000 --> 00:04:54,000
Take out the collection as my argument.

75
00:04:54,000 --> 00:04:58,000
If you want, you can keep only elements that are present in both collections.

76
00:04:58,000 --> 00:05:04,000
To do this, we have to invoke retain all methods and positive reference to another collection into

77
00:05:04,000 --> 00:05:04,000
it.

78
00:05:05,000 --> 00:05:11,000
In other words, this message removes from the current collection all elements that are not present

79
00:05:11,000 --> 00:05:17,000
in the collection that we passed as a method augment the methods that are left here are also describing

80
00:05:18,000 --> 00:05:23,000
claims method will remove all elements from the collection and as you already know, equals and harsh

81
00:05:23,000 --> 00:05:26,000
methods that are the methods that each object should have.

82
00:05:27,000 --> 00:05:33,000
But the idea of specifying equals and Haskett methods in the collection interface is to put stress on

83
00:05:33,000 --> 00:05:39,000
the fact that these methods should be implemented in an implementation of collection interface and that

84
00:05:39,000 --> 00:05:43,000
these methods should override default behavior from object class.

85
00:05:43,000 --> 00:05:48,000
And the last but not the least, massive collection interface is an iterator.

86
00:05:48,000 --> 00:05:51,000
Pay attention to the iterable interface description now.

87
00:05:52,000 --> 00:05:57,000
It is also the collection interface because it implements a terrible interface.

88
00:05:57,000 --> 00:06:03,000
As you can see, Iterator method returns object of iterator type insert.

89
00:06:03,000 --> 00:06:07,000
This object will help you to iterate over each element in your collection.

90
00:06:07,000 --> 00:06:13,000
We are going to learn what Iterator is in the separate class and that is how our collection interface

91
00:06:13,000 --> 00:06:14,000
that is something.

92
00:06:14,000 --> 00:06:15,000
What do you have to remember?

93
00:06:16,000 --> 00:06:21,000
We just have such interface and what we can do is just to remember it just as an alphabet.

94
00:06:21,000 --> 00:06:26,000
We don't ask why a letter is written exactly in this way.

95
00:06:26,000 --> 00:06:30,000
We just learned that this is a letter and how it sounds.

96
00:06:30,000 --> 00:06:36,000
And when we know that we start building words with this letter, the same as here, we just have to

97
00:06:36,000 --> 00:06:38,000
learn collection, interface and learn how to use it.

98
00:06:39,000 --> 00:06:45,000
So here on the screen, you may see only abstract methods that should be implemented in each collection,

99
00:06:45,000 --> 00:06:49,000
but there are a few more other default methods in the collection interface.

100
00:06:49,000 --> 00:06:55,000
What are they to answer this question and to give you otherwise how constantly learn new things and

101
00:06:55,000 --> 00:07:00,000
check information that you get not only on this lesson but in any tutorial?

102
00:07:00,000 --> 00:07:03,000
Always investigate the source code of your conversion.

103
00:07:04,000 --> 00:07:09,000
I believe you remember how to add source code, your code editor and where you might find it.

104
00:07:09,000 --> 00:07:14,000
Let's open collection type to investigate the source code and find methods that we didn't learn yet.

105
00:07:15,000 --> 00:07:20,000
I press control shift and simultaneously I have to type collection.

106
00:07:21,000 --> 00:07:27,000
I need collection from Java with your package and here this and here on the right, we might see a list

107
00:07:27,000 --> 00:07:30,000
of all methods that are present in this interface.

108
00:07:30,000 --> 00:07:34,000
It looks like we went over all abstract methods.

109
00:07:34,000 --> 00:07:40,000
How I learned which method is abstract and it's is a small a letter that stands for abstract.

110
00:07:41,000 --> 00:07:45,000
But we didn't cover in our presentation methods that have Glitnir.

111
00:07:45,000 --> 00:07:46,000
What are they?

112
00:07:47,000 --> 00:07:50,000
Here's the overloaded method to array it.

113
00:07:50,000 --> 00:07:57,000
Just take specific functions that will describe how to convert collection to a right to be able to apply

114
00:07:57,000 --> 00:07:57,000
this method.

115
00:07:57,000 --> 00:08:03,000
We have to know how to write in the functional style in Java and understand what functional interface

116
00:08:03,000 --> 00:08:03,000
is.

117
00:08:04,000 --> 00:08:05,000
Don't worry.

118
00:08:05,000 --> 00:08:08,000
This topic also will be discussed in the separate lesson.

119
00:08:08,000 --> 00:08:13,000
I just want you to understand, at least on the high level, what these default methods are about.

120
00:08:13,000 --> 00:08:21,000
Remove method, this method takes predicate, predicate is a specific type that can return true or false

121
00:08:22,000 --> 00:08:26,000
based on the specific function that you will pass as a method argument to this method.

122
00:08:26,000 --> 00:08:29,000
It will identify which element should be removed.

123
00:08:29,000 --> 00:08:32,000
For example, you may describe functions that will return.

124
00:08:32,000 --> 00:08:38,000
True in a case product price is more than one hundred dollars, and in case this function will be applied

125
00:08:38,000 --> 00:08:44,000
to this specific product and collection, it will be removed and this function will be applied to each

126
00:08:44,000 --> 00:08:50,000
element in the collection you might find while loop here and see that Iterator is used to go over the

127
00:08:50,000 --> 00:08:56,000
collection as a condition for each element in the collection and remove it in case it satisfies the

128
00:08:56,000 --> 00:08:57,000
condition.

129
00:08:57,000 --> 00:09:01,000
Also, there is a default method that creates iterator.

130
00:09:01,000 --> 00:09:07,000
Split Iterator is a specific type that can traverse and make parts of elements of the source collection.

131
00:09:08,000 --> 00:09:11,000
And here is a method that exists in all implementations of collection.

132
00:09:11,000 --> 00:09:18,000
Interface Stream Method joins the collection into stream of elements or in other words, sequential

133
00:09:18,000 --> 00:09:19,000
stream of elements.

134
00:09:20,000 --> 00:09:26,000
String Mapei was introduced in Java version eight and it was a breakthrough in this course in separate

135
00:09:26,000 --> 00:09:31,000
lesson will be on stream API and we'll learn how to use it as a practical exercise.

136
00:09:31,000 --> 00:09:35,000
Will even rewrite our home tasks with the help of the Stream API.

137
00:09:36,000 --> 00:09:38,000
And here is a massive, transparent stream.

138
00:09:39,000 --> 00:09:44,000
According to documentation, it returns possible parallel stream with the current collection at its

139
00:09:44,000 --> 00:09:44,000
source.

140
00:09:46,000 --> 00:09:51,000
Now, let's recap what we have learned today, so they've learned what the connection is, we try to

141
00:09:51,000 --> 00:09:54,000
imagine collection is a back for our understanding.

142
00:09:55,000 --> 00:09:59,000
The day you saw your first UML diagram, class diagram.

143
00:09:59,000 --> 00:10:05,000
Now you know how to read class diagrams to understand the type of description we reviewed all abstract

144
00:10:05,000 --> 00:10:07,000
methods in collection interface.

145
00:10:07,000 --> 00:10:10,000
And after that, we reviewed the collection before methods.

146
00:10:10,000 --> 00:10:14,000
Also during the lesson we investigated source code of collection interface.

147
00:10:15,000 --> 00:10:17,000
That's all what I have for you for today.

148
00:10:17,000 --> 00:10:18,000
Thanks a lot for your attention.

149
00:10:18,000 --> 00:10:20,000
See you in the next lesson.