Example of abstract class in java

    // A Simple demonstration of abstract.

    abstract class A
    {
    // abstract method in abstract class
    abstract void callme();
    // concrete methods are  allowed in abstract classes
    void callmetoo()
    {
    System.out.println("This is a concrete method.");
    }
    }
    // class B extends the absract class A
    class B extends A {
    void callme() {
    System.out.println("B's implementation of callme.");
    }
    }

    class AbstractDemo {
    public static void main(String args[]) {
    B b = new B();
    b.callme();
    b.callmetoo();
    }
    }