1
00:00:01 --> 00:00:05
Welcome to the Spoken Tutorial on method overloading in java.

2
00:00:06 --> 00:00:07
In this tutorial we will learn:

3
00:00:08 --> 00:00:09
* What is method overloading.

4
00:00:10 --> 00:00:12
* And 	to overload method.

5
00:00:13 --> 00:00:23
Here we are using:

 Ubuntu version 11.10  OS

 Java Development kit 1.6

 And Eclipse 3.7.0

6
00:00:24 --> 00:00:25
To follow this tutorial, you must know

7
00:00:26 --> 00:00:28
how to create methods and

8
00:00:29 --> 00:00:31
to overload constructor in java using eclipse.

9
00:00:32 --> 00:00:38
If not, for relevant tutorials, please visit our website which is as shown.
http://www.spoken-tutorial.org

10
00:00:39 --> 00:00:41
What is method overloading?

11
00:00:42 --> 00:00:45
Define two or more methods with same name within a class.

12
00:00:46 --> 00:00:49
They must differ in number or types of parameters.

13
00:00:50 --> 00:00:53
These methods are called overloaded methods.

14
00:00:54 --> 00:00:56
The process is called method overloading.

15
00:00:57 --> 00:00:59
Let us now see how to overload a method.

16
00:01:00 --> 00:01:05
In eclipse, I have a class Addition.

17
00:01:06 --> 00:01:09
Inside the class,  we will  declare two integer variables.

18
00:01:10 --> 00:01:18
So, type: int a is equal to 10 and int b is equal to 5.

19
00:01:19 --> 00:01:22
Let us create a method to add these two integers.

20
00:01:23 --> 00:01:29
So, type:  void add parentheses.

21
00:01:30 --> 00:01:39
Within curly brackets, type: System dot out dot println.

22
00:01:40 --> 00:01:43
Inside  parentheses a+b.

23
00:01:44 --> 00:01:49
So, this method will give us the sum of two integer variables.

24
00:01:50 --> 00:01:54
Let us create another method which takes two parameters.

25
00:01:55 --> 00:02:03
So, type: void addTwoNumbers.

26
00:02:04 --> 00:02:13
Within parentheses int num1 comma int num2.

27
00:02:14 --> 00:02:34
Then, within curly brackets System dot out dot println num1 plus num2.

28
00:02:35 --> 00:02:43
So, this method will give us the sum of two  values that are passed as arguments to this method.

29
00:02:44 --> 00:02:48
Let us create an object of the class and call the methods.

30
00:02:49 --> 00:03:12
So, in  the  Main method  type: Addition i.e the class name  obj is equal to new Addition parentheses semicolon.

31
00:03:13 --> 00:03:17
Then Obj.add

32
00:03:18 --> 00:03:30
And Obj.addTwonumbers  within parentheses.

33
00:03:31 --> 00:03:32
we  will pass  two arguments.

34
00:03:33 --> 00:03:36
Suppose if we pass floating point values.

35
00:03:37 --> 00:03:44
So, type 2.5 comma and an  integer 3.

36
00:03:45 --> 00:03:56
We get an error which states that:  the method addTwoNumbers  int comma int  of the  class addition is not applicable for the arguments double comma int.

37
00:03:57 --> 00:04:05
So, what we do is, in the method instead of int we will give double.

38
00:04:06 --> 00:04:11
So replace int by double . Save the file.

39
00:04:12 --> 00:04:16
we see that the error is resolved.

40
00:04:17 --> 00:04:23
we also  know that Java automatically i.e. implicitly coverts int into double.

41
00:04:24 --> 00:04:27
So, here we can pass integer arguments as well.

42
00:04:28 --> 00:04:31
Now  Save and Run the program.

43
00:04:32 --> 00:04:36
In the output, we see the sum of two integer variables

44
00:04:37 --> 00:04:42
and the sum of two numeric arguments that we passed.

45
00:04:43 --> 00:04:49
Now we see that both the methods perform same operation.

46
00:04:50 --> 00:04:59
The difference is that the first method  has no parameter while the second method has  parameters.

47
00:05:00 --> 00:05:04
So, in such cases java provides us with method overloading.

48
00:05:05 --> 00:05:08
So, what we do is, give same name to both the methods.

49
00:05:09 --> 00:05:28
So, replace addTwoNumbers with add; also change here.

50
00:05:29 --> 00:05:32
We will define one more method with same operation.

51
00:05:33 --> 00:05:37
So, type: void add.

52
00:05:38 --> 00:05:50
And within parentheses int n1 comma int n2 comma int n3.

53
00:05:51 --> 00:05:53
So we have given three parameters.

54
00:05:54 --> 00:06:02
Then, within curly brackets System dot out dot println.

55
00:06:03 --> 00:06:10
Within parentheses n1 plus n2 plus n3.

56
00:06:11 --> 00:06:16
So, this method will give sum of three numbers.

57
00:06:17 --> 00:06:18
Let us call this method.

58
00:06:19 --> 00:06:34
So, type: obj dot add 1 comma 5 comma 4.

59
00:06:35 --> 00:06:46
Save and Run.

60
00:06:47 --> 00:06:51
So, Java compiler overloads the proper method depending on the parameters.

61
00:06:52 --> 00:06:56
It checks the number and type of parameters passed.

62
00:06:57 --> 00:07:00
So, as a programmer we don't have to worry about the method name.

63
00:07:01 --> 00:07:04
Nor even the type or number of arguments we  passed.

64
00:07:05 --> 00:07:10
We can create one more method which appends strings.

65
00:07:11 --> 00:07:14
So we will create one more overload  method.

66
00:07:15 --> 00:07:28
Type: void add String s1 comma String s2.

67
00:07:29 --> 00:07:40
Within curly brackets System dot out dot println.

68
00:07:41 --> 00:07:44
Within parentheses s1 plus s2.

69
00:07:45 --> 00:07:49
And we will call  this method.

70
00:07:50 --> 00:07:54
So, type: obj dot add.

71
00:07:55 --> 00:08:06
Within parentheses in double quotes Hello comma in double quotes space World.

72
00:08:07 --> 00:08:11
Now   Save and Run the program.

73
00:08:12 --> 00:08:15
So, in the output we see Hello space World.

74
00:08:16 --> 00:08:20
So, the add method with two string arguments, appends the string.

75
00:08:21 --> 00:08:26
Suppose now we declare add method with return type.

76
00:08:27 --> 00:08:39
So, type: int add parentheses  no  parameter and curly brackets.

77
00:08:40 --> 00:08:47
We get an error.  It states that duplicate method add in type addition.

78
00:08:48 --> 00:08:53
This is because we have already declared a   method add with no parameters.

79
00:08:54 --> 00:08:57
So, remember that to overload a  method, the parameters must differ.

80
00:08:58 --> 00:09:02
Having different return types will not overload the method.

81
00:09:03 --> 00:09:08
So, remove this method  and Save the file.

82
00:09:09 --> 00:09:15
This is how method overloading is done in java.

83
00:09:16 --> 00:09:17
So, in this tutorial we learnt:

84
00:09:18 --> 00:09:19
* About method overloading.

85
00:09:20 --> 00:09:21
* To overload method.

86
00:09:22 --> 00:09:24
* And advantage of method overloading.

87
00:09:25 --> 00:09:30
For self assessment: create a method subtract that subtracts number,

88
00:09:31 --> 00:09:32
overload it.

89
00:09:33 --> 00:09:35
To know more about the Spoken Tutorial project,

90
00:09:36 --> 00:09:41
watch the video available at [1]

91
00:09:42 --> 00:09:44
It summarizes the Spoken Tutorial project.

92
00:09:45 --> 00:09:47
If you do not have good bandwidth, you can download and watch it.

93
00:09:48 --> 00:09:49
The Spoken Tutorial project team:

94
00:09:50 --> 00:09:51
Conducts workshops using spoken tutorials.

95
00:09:52 --> 00:09:55
Gives certificates to those who pass an online test.

96
00:09:56 --> 00:10:00
For more details, please write to contact@spoken-tutorial.org

97
00:10:01 --> 00:10:04
Spoken Tutorial Project is a part of the Talk to a Teacher project.

98
00:10:05 --> 00:10:10
It is supported by the National Mission on Education through ICT, MHRD, Government of India.

99
00:10:11 --> 00:10:18
More information on this mission is available at
[2].

100
00:10:19 --> 00:10:20
We have come to the end of this tutorial.

101
00:10:21 --> 00:10:21
Thanks for joining.

102
00:10:22 --> 00:10:27
This is Prathamesh Salunke, signing off.  Jai Hind.