Methods in Java

What is a method in java?

Method is a collection of executable java statements. In other words, method acts as a container for different java statements. In java, methods mainly perform the operations on data. Methods are

• The advantage of creating a method is code re-usability which means write once and execute multiple times.
• Methods make modifications easy.
• It makes code easy to read and understand.
• Creating methods reduces boiler-plate code

Types of Methods in Java

Methods are mainly classified into two types: Pre-defined( Internal) and User-defined (External) methods

Predefined Methods:

• Predefined methods (internal methods or inbuilt methods) are already declared in java
• JVM automatically executes the internal methods
• Developer cannot make any changes into internal methods.

User defined Methods:

• If a developer creates a method then it is an external methods or user defined method.
• Developer can create any number of external methods.
• By creating external methods we develop modular code(source code which is easy to maintain and test).

Declaration of methods in Java

Method declaration is done within a class. Methods are declared using multiple components. Generally, the components in a method are method signature and method body. Method body consists of executable java statements and Method signature consists of the following components:

1. Access modifier:

   • Access modifiers are used to apply visibility restrictions on members of the class.

2. Non access modifier:

   • Non-access modifiers change the behavior of member but it will not affect the visibility of that method.
   • Following are the non-access modifiers in Java.
     • static
     • abstract
     • final

3. Return type:

   • Return type in java indicates the type of value which a method returns.
   • Void method:
     • If the method is having return type as void then we cannot transfer the data from that particular method.
   • Non void method:
     • If the method contains the return statement then it will be considered as non void method.
     • It is possible to transfer the data from one method to another method with the help of return statement.
     • If the method is having return statement then we have to use appropriate datatype as a return type.
     • Return statement should be the last statement of method body.

4. Method name:

   • Method declaration also consists of method name. Method naming is done using any identifier.
   • As java supports method overloading and method overriding, multiple methods can share same name.

5. Parameters:

   • Parameterized method:
     • The method which accepts input parameter is a parameterized method.
     •  Number of arguments should be same as that of the number of parameters at the time of method call.

     • Example for Parameterized Method

       class MethodDemo{
           
           public static void main(String[] args){
                addition(10,20,30);
           }
           //external method
           public static void addition(int a,int b, int c){
               System.out.println("Addition :"+(a+b+c));
           }
       
       }

   • Non parameterized method:
     • The method which does not accept input parameters is a non parameterized or zero parameterized method.
     • We cannot pass any arguments to the non parameterized method.

     • Example for Non Parameterized method

       //Calculate Area of Circle
       class MethodDemo{
       
         static double radius=12.0;
         
         public static void main args(String[] args){
             calculateArea();
         }
       
         public static void calculateArea(){
             double area=3.14*radius*radius;
             System.out.println("Area of Circle is : "+area);
         }
       
       }