public class Test {

    public static void main(String[] args){

        A a = new A();
        a.printMe();
        //a.doSomethingElse();
        // Prints "A"

        B b = new B();
        b.printMe();
        // Prints "B"
        b.doSomethingElse();

        A a2 = new B();
        a2.printMe();
        // Prints...? "B"
        //a2.doSomethingElse(); // Doesn't work
        ((B) a2).doSomethingElse(); // Works with casting
        // Equivalent to...
        B b2 = (B) a2;
        b2.doSomethingElse();
        // The above could throw ClassCastException if a2 is not type "B"

        a2 = new C();
        a2.printMe();
        // Prints... "C"

    }

    static class A extends Object /* implied */ {
        public void printMe() {
            System.out.println("A");
        }
        @Override
        public String toString() {
            return "A";
        }
    }
    static class B extends A {
        @Override // Override's A's printMe() method
        public void printMe() {
            System.out.println("B");
        }

        public void doSomethingElse() {

        }
    }
    static class C extends A {
        @Override
        public void printMe() {
            System.out.println("C");
        }
    }
}