/*
  An example from Java: A beginners's guide by Herbert Schildt that
  illustrates the the strongly typed nature of Java.  A reference for one
  type of object cannot normally refer to another type of object except
  whne a reference of a superclass is referred to an object that's a
  subclass.
  v1 - won't compile.
  v2 - uses inheritance and will compile
*/
public class Driverv2
{
    public static void main (String [] args)
    {
	Xv2 x = new Xv2(10);
	Xv2 x2;
	Yv2 y = new Yv2(5,6);
	x2 = x;     // OK, both of the same type
	System.out.println("x2.a: " + x2.getA());

	x2 = y;   // Still okay because y is derived from x
	x2.setA(19);

	// x2.setB(27);  // Not okay because X doesn't have this method.
    }
}