Inheritance

[archu sweet]

 class ClassA {}
 class ClassB extends ClassA {}
 class ClassC extends ClassA {}
and:
ClassA p0 = new ClassA();
ClassB p1 = new ClassB();

I want to know how come p0=p1 is true ??

[Jesper de Jong]

I guess you mean p0 == p1, because p0 = p1 is not a boolean expression.

Why do you think it is true? Did you try this code out?

[archu sweet]

yes i meant p0 == p1...i tried out it says it is valid....but they belong to different classes how can they be equal ??

[Matthew Brown]

It's valid to compare them, because a ClassB IS-A ClassA. Which means that it's possible for ClassA and ClassB references to be equal. For example:

ClassB p0 = new ClassB();
ClassA p1 = p0; // OK because ClassB extends ClassA

Then p0 == p1 is true.

The compiler will only stop you comparing them if they can't possibly be equal.

[Unnar Björnsson]

p0 and p1 are not equal, what makes you think they are?