Some times we can declare a class inside another class such type of classes are called inner classes

        Example

        Class Car{

      //more code here

      Class Engine{

            //more code here

      }

     }

Without existing Car object there is no chance of existing Engine object, hence Engine class has declared inside Car class. 
 

There are four types of inner classes are present 

• Normal or regular inner class
• Method local inner class
• Anonymous inner class
• Static nested  class

• Sometimes we can declare a class inside a method such type of classes are called method local   

inner  classes

The scope of method local inner classes is the scope of the method where it is declared.

           Example 

           class Test{

      public  void  m1(){

               class Inner {

                               public void sum(int I,int j){

                  System.out.println(i+J);

            }//sum

             }//inner

            Inner  i=new Inner();

            i.sum(10,20);

            //more code here  

           I.sum(100,303);

           //more code here 

         i.sum(102,84);

        }//m1()

   Public  static  void main(){

      New Test().m1();

}

}  
 

anonymous inner classes

            ANONYMOUS INNER CLASS THAT EXTENDS A CLASS

            Example

            Class popcorn{

                  Public void taste(){

                        System.out.println(“it is salty”);

                  }

                  //more code here

            } 

            Class Test{

                  Public static void main(String[] args)

                        {

                        Popcorn p=new Popcorn()

                        {    // here we are creating child class for popcorn

      Public void taste(){

      System.out.println(“it is sweet”);

                              }

};//here semicolon indicates we r creating child class object with parent    

// class reference here child class dosent contain name

                  p.taste()// it is sweet

                  Popcorn p=new Popcorn();

                  p1.taste() //it is salty

                  }

            } 
 
 

ANONYMOUS INNER CLASS THAT IMPLEMENTS AN INTERFACE

example 

      class Test{

               Public static void main(String[] args){

            Runnable r=new Runnable(){

                  Public void run(){

                         for(int i=0;i<10;i++){

                        System.out.printin(“child thread”);

       }

}

            };

      Thread t=new Thread(r);

            t.start();

            for(int i=0;i<10;i++){

                  System.out.printin(“main thread”);

      }

      }

      }

      Don’t become fool that here we are creating object of interface Runnable.Here we are actually

               creating an object of class that is  implemented Runnable interface. 

      ANONYMOUS INNER CLASS THAT DEFINES INSIDE A METHOD ARGUMENT

      Example

      Class Test{

                      Public static void main(String[] args){

                  New Thread(new Runnable()

                                                                       {

                                    Public void run(){

                                    for(int i=0;i<10;i++){

                                          System.out.printin(“child thread”);

          } 

                                    }

                                     }).start();

                              for(int i=0;i<10;i++){

                  System.out.printin(“main thread”);

                     }

                  }//main

            }//Test 
 
 

   By using parent class names