Abstract class in Java

• Abstraction is a process of hiding the implementation details and showing only functionality to the user.
• Abstraction lets you focus on what the object does instead of how it does it
• An abstract class may or may not have an abstract method.
• There is no object creation for Abstract class. It should only be implemented and used by the subclass.
• A subclass which inherits the abstract class either has to implement all the abstract methods present in the abstract class or declare itself as abstract.
• It is like interface but it can have other method definitions apart from abstract method.
• Abstract method is a method which has no implementation only declaration.

abstract void method();

Example:

package Mypkg;
public class myabs {
      /**
       * @param args
       */
      public static void main(String[] args) {
            // TODO Auto-generated method stub
        System.out.println("Entered myabs-Main() ");
        System.out.println("***************************************");
            useabs ob=new useabs();
            ob.getDisplay();
            ob.getD();
        System.out.println("***************************************");
        System.out.println("Exited  myabs-Main() ");
      }
}
abstract class myabsEx
{
      abstract void getDisplay(); // Abstract method
      void getD() // other method
      {
            System.out.println("This is normal method inside Abstract class");
      }
}
class useabs extends myabsEx
{      void getDisplay()
      {
            System.out.println("This is re Definition given of  Abstarct method class");
      }
}

Output :

Entered myabs-Main()

***************************************

This is re Definition given of  Abstarct method class

This is normal method inside Abstract class

***************************************

Exited  myabs-Main()

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