Q 10) Abstract Class

Abstract Class:

• Creation of a super class that only defines a generalized form (features of different sub classes) that will be shared by all of the sub classes, where in the subclass will fill up rest of the details.
• An abstract class is a class that is declared with an “ abstract “ keyword.
• An abstract class in never " Instantiated " meaning an instance of abstract class cannot be created.
• It can have both abstract and non-abstract methods (methods without body and concrete methods).
• Abstract Classes can have Constructors, member variables and normal (concrete) methods.
• It is used to provide Abstraction.
• Abstract Classes are not Interfaces.

Syntax of Abstract Class:

abstract class class – name {

     }

Abstract Method:

·       A method that is declared without any body within an abstract class is known as Abstract method.

·       The method can be defined by its sub class.

·       Abstract methods can never be final or static.

·       Any class that extends abstract class must implement all the abstract methods declared by the super class or make the child class abstract.

Abstract Method Syntax:

abstract return_type method_name();

//No definition.

Example Program of Abstract Class:

package org.javanoobs.abstractdemo;

public abstract class A {

    

     // This is the abstract method..

     abstract void callMe();

    

     //This is the normal or concrete method..

    

     public void normal(){

          

           System.out.println(" This is the normal or concrete method.. ");

     }

    

    

}

package org.javanoobs.abstractdemo;

public class B extends A {

     void callMe(){

          

           System.out.println(" This is the abstract call me method !!! ");

     }

    

public static void main(String[] args) {

    

    

     B b = new B();

     b.callMe();

     b.normal();

}

}

OUTPUT :

This is the abstract call me method !!!

This is the normal or concrete method..