package corejava; abstract class A { abstract void callme(); // Concrete methods are still allowed in abstract classes void demo() { System.out.println("This is a concrete method"); } } class B extends A { void callme() { System.out.println("B class' implementation of callme"); } } public class DemoAbstract { public static void main(String args[]) { B b = new B(); b.callme(); b.demo(); } }