NESTED AND INNER CLASSES

NESTED CLASS : CLASS CREATED WITHIN A CLASS

PROGRAM FOR NESTED CLASS

public class outer {

      int x =10;

     

      void fun(){

            inner i1 = new inner();

            i1.display();

      }

     

     

      class inner{

            int y =200;

           

            void display(){

                  System.out.println("x = "+x);

            }

      }

     

      void showy(){

            System.out.println("y ="+y);     // error //

      }

      public static void main(String[] args) {

           

            outer o1 = new outer();

            o1.fun();

           

      }

}

OUTPUT : X=10

BUT Y CAN'T BE ACCESSED AS OUTER CLASS CANNOT ACCESS INNER CLASS DE VARIABLES

ADVANTAGES OF NESTED CLASSES : 

1. HERE, INNER CLASS CAN ACCESS ALL MEMBERS OF OUTER CLASS INCLUDING OUTER                                                           CLASS VARIABLES AND METHODS.

2. IT MAKES CODE MORE READABLE

3. IT MAKES CODE MORE MAINTAINABLE

4. CODE OPTIMIZATION : MEANS IT NEED LESS CODE TO WRITE

DIFFERENCE BETWEEN INNER CLASS AND NESTED CLASS

* NESTED CLASS CAN BE STATIC AS WELL AS NON - STATIC.BUT INNER CLASS IS ALWAYS NON - STATIC

TYPES OF INNER CLASSES:  3 TYPES

1. MEMBER INNER CLASS : CLASS CREATED WITHIN CLASS AND OUTSIDE OUTER CLASS        METHOD.

2.ANNONYMOUS INNER CLASS : CLASS CREATED FOR IMPLEMENTING INTERFACE OR EXTENDING CLASSES

3. LOCAL INNER CLASS : INNER  CLASS CREATED WITHIN  OUTER  CLASS METHOD