Superclass reference calls subclass's method..

Question

I have a doubt regarding the following..
class A //super class
    public void ShowMessage()
        System.out.println("Inside A's showmessage");
class B extends A //subclass
    public void ShowMessage()
        System.out.println("Inside B's showmessage");
    public void ShowAnotherMessage()
        System.out.println("Inside B's showanothermessage");
class MainClass
    public static void main(String args[])
        A a; //plain reference
        B b=new B();
        a=b;
        a.ShowAnotherMessage(); //error, since it is not part of
A
        a.ShowMessage(); //Actually calls B's version
1. How do i make it call a's ShowMessage(). Is it possible with some typecast. What are the ways to call A's ShowMessage().
2. The above is not a problem in C++, can use virtual functions to do it.
[b]
thanks...

Answer 1

The behaviour you observe is correct. When a method is invoked the actual class of the object is used, when a variable is referenced the type of the reference determines the class. See section 3.3.3 of "The Java Programming Language" for more details. In C++ you must declare the method virtual to get this behaviour, in Java all methods are virtual.