abstract class Base// Abstract Class Declaration. { abstract void fun();// Abstract Method Declaration. } class Demo extends Base// Demo class Inharit Base Class. { void fun()//Concreat Method declaration or Overriding fun() method. { System.out.println("Demo fun() Method Calling"); } } class Example_Abstract_Class_Base { public static void main (String []args) { Base b= new Demo(); b.fun(); } }