Methods, Method overloading

Methods in java

A Java method is a collection of statements that are grouped together to perform an operation. When you call the System.out.println method, for example, the system actually executes several statements in order to display a message on the console.

Now you will learn how to create your own methods with or without return values, invoke a method with or without parameters, overload methods using the same names, and apply method abstraction in the program design.

Declaration of methods

access_modifier return_type  name_of_method(parameter List)

{

    //method body

}

Method Overloading 

Method Overloading:-If a class have multiple methods by same name but different parameters, it is known as Method Overloading.

Method overloading can be done by two ways:-

1. By changing number of arguments

       class Calculation{  

       void sum(int a,int b){System.out.println(a+b);}  

       void sum(int a,int b,int c){System.out.println(a+b+c);}  

  

       public static void main(String args[]){  

       Calculation obj=new Calculation();  

       obj.sum(10,10,10);  

       obj.sum(20,20);  

  

  }  

}  

  output: 30

              40

1. By changing data type

         class Calculation2{  

         void sum(int a,int b){System.out.println(a+b);}  

         void sum(double a,double b){System.out.println(a+b);}  

  

         public static void main(String args[]){  

         Calculation2 obj=new Calculation2();  

         obj.sum(10.5,10.5);  

         obj.sum(20,20);  

  

  }  

}  

output:21

          40

Note: Method overloading is not possible by changing return type because they may cause ambiguity.

Can we overload main method() ?

Ans:- Yes, main method can be overloaded. You can any number of main() methods in a class by method overloading.

Example:-

                     class Overloading1{  

                           public static void main(int a){  

                                   System.out.println(a);  

                           }  

    

                          public static void main(String args[]){  

                                  System.out.println("main() method invoked");  

                                  main(10);  

                           }  

                   }  

output: main() method invoked

            10