Explain the ouput

[B pandoo]

class A{
int x= 5;
}
class B extends A{
int x =6;
}


public class CovariantTest
{
public A getobject(){
return new A();
}
public static void main(String[] args)
{
CovariantTest c = new SubCovariant();
System.out.println(c.getobject().x);
}

}

class SubCovariant extends CovariantTest{

public B getobject(){
return new B();
}

}
Answer is 5.

please explain this answer.when c.getobject() is called, at runtime ,it will select the SubCovariant class method and since it returns B's object,we should get the answer as B.x = 6 right.if i am wrong please correct me.

[James Quinton]

Which variable is used is determined by reference type, not implementation type. This is very opposite to method invocation. When you say A a = new B(); Class A's variables will be referred even though the underlying implementation is B class. But B's methods will be invoked.

In your case, when you invoke SubCovariant.getObject(), you get B object, but it's casted to A because your reference type is the superclass. So when you call .x, you actually get A's x, not B.
[ November 14, 2006: Message edited by: James Quinton ]

[anvesh charuvaka]

The polymorphism as you perceive it works only with methods.

When you access an instance variable through a reference then
the variable you access depends on the type of Reference you are using and not
the run time object stored int the reference variable.