Overriding

[Renjith Mohan]

  class A{

void meth(){
System.out.println("parent");
}

}

class B {
void meth(){
System.out.println("overriden");
}
}

class OverrideDemo{

public static void main(String sp[]) {
B obj = new A(); //why it fails here?
}

}  

Even if I downcast to class B, it fails. What exactly is the reason behind this?

Thanks in advance
Renjith

[Rahul Nair]

It is natural that, B can do all the stuff that A can, But the reverse is not true. As 'obj' reference is is pointing to the Object of type A, So if 'obj' is calling the B specific stuff on object of type A, then obviously it will not be able to do it. because it is referring the object of type A. That is why, it fails.

The downcast is fails, because A never does the B specific stuff.

Please check it here, the question is already answered.

[Seetharaman Venkatasamy]

Renjith Mohan wrote: What exactly is the reason behind this?

B is-a A , but reverse not[A is not B].

[David Newton]

There is *no* relationship between A and B other than they both declare a method of the same name.

There are no subclasses, no interfaces, is-a relationship. They are completely unrelated classes, hence no type conversion is possible.

[Rahul Nair]

Yes David, you are correct! I have not seen it. Sorry for mislaid.

[Seetharaman Venkatasamy]

Rahul Nair wrote:Yes David, you are correct! I have not seen it. Sorry for mislaid.

me too :shock:

[Henry Wong]

The original answer "A is NOT B" still stands. This just adds "B is also NOT A" to that conclusion.

Henry

[Arun C. Giridharan]

basically ...you can't override .. class A is different and class B is different ....(yea..No inheritance)...