10 - Methods in Java/004 Variable Length Arguments_en.srt

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

2
00:00:00,000 --> 00:00:04,000
Today we will discuss what are variable length arguments in Java.

3
00:00:04,000 --> 00:00:06,000
Let's start from the problem statement.

4
00:00:06,000 --> 00:00:11,000
You want to create method, but you don't know how much arguments will be passed to that method.

5
00:00:11,000 --> 00:00:16,000
There can be different business cases, but let's simplify and pretend that you need to create method

6
00:00:16,000 --> 00:00:22,000
which will some numbers, but you don't know how much numbers will be passed to this method.

7
00:00:22,000 --> 00:00:27,000
To not create method which returns sum of two numbers, and another method which returns sum of three

8
00:00:27,000 --> 00:00:31,000
numbers, and so on, you create one method with variable length arguments.

9
00:00:31,000 --> 00:00:33,000
The syntax is simple.

10
00:00:33,000 --> 00:00:36,000
You need to specify type of arguments, right?

11
00:00:36,000 --> 00:00:38,000
Ellipses and variable name.

12
00:00:38,000 --> 00:00:41,000
Inside the method you can treat this variable as array.

13
00:00:42,000 --> 00:00:46,000
This syntax will allow you to pass different amount of arguments to the method.

14
00:00:46,000 --> 00:00:51,000
Here you can see that I pass five integers and here I pass just one argument.

15
00:00:51,000 --> 00:00:55,000
In both cases this method is called and result is returned.

16
00:00:55,000 --> 00:01:00,000
You can even change the way how you declare a main method instead of specifying that the main method

17
00:01:00,000 --> 00:01:06,000
takes an array of strings, we can say that the main method can work with variable length arguments

18
00:01:06,000 --> 00:01:10,000
of type string declaration like this is also possible.

19
00:01:10,000 --> 00:01:15,000
Important thing to flag here is that variable length arguments should be declared as last parameter

20
00:01:15,000 --> 00:01:16,000
in the method.

21
00:01:17,000 --> 00:01:22,000
For example, this method declaration will produce compilation error because the variable argument type

22
00:01:22,000 --> 00:01:25,000
int of the method must be the last parameter.

23
00:01:25,000 --> 00:01:31,000
Because during runtime, JVM should know when int arguments are finished and strings are started, and

24
00:01:31,000 --> 00:01:36,000
when we adjusted the method declaration, everything is fine and there is no compilation error.

25
00:01:37,000 --> 00:01:41,000
Variable length argument always should be declared as the last parameter in the method.

26
00:01:41,000 --> 00:01:47,000
You already saw real life example of variable length argument, but probably didn't pay enough attention.

27
00:01:47,000 --> 00:01:50,000
Do you remember lesson about string formatting?

28
00:01:50,000 --> 00:01:56,000
Method format takes variable length arguments as a parameter, because we never know how much format

29
00:01:56,000 --> 00:01:59,000
specifiers will be present in string, which we need to format.

30
00:02:00,000 --> 00:02:04,000
That's all what I wanted to share with you regarding variable length arguments.

31
00:02:04,000 --> 00:02:08,000
Now let's recap what you have learned about methods in this section.

32
00:02:08,000 --> 00:02:10,000
You learned how to declare and call methods.

33
00:02:10,000 --> 00:02:14,000
You understand what method signature is and how we can overload methods.

34
00:02:14,000 --> 00:02:20,000
Now you understand that both reference and primitive types of data in Java are passed by values.

35
00:02:20,000 --> 00:02:26,000
During the method invocation, we wrote recursive methods and learn what variable length arguments are.

36
00:02:26,000 --> 00:02:28,000
Let's take a look at your homework now.

37
00:02:29,000 --> 00:02:32,000
Your homework primarily consists of coding exercises.

38
00:02:32,000 --> 00:02:38,000
Now when you know how to write custom methods, how to use loops, arrays, and primitive types of data,

39
00:02:38,000 --> 00:02:41,000
our tasks might become a little more complicated.

40
00:02:41,000 --> 00:02:45,000
I tried to describe homework with as much details as I could.

41
00:02:45,000 --> 00:02:47,000
Try to solve these tasks.

42
00:02:47,000 --> 00:02:52,000
I will share with you source code of the solution for these tasks, but try to solve them by yourself

43
00:02:52,000 --> 00:02:53,000
first.

44
00:02:53,000 --> 00:02:56,000
Thanks a lot for your attention and see you in the next lesson.