Casting question

[Sani babangida]

I have two classes that are identical . they both extend a class A

b ---extends -->A
c ---extends--->A

is it possible to cast from b to c

[Ernest Friedman-Hill]

No, it's not possible. In C++, you can get away with this by using an "old-style" cast; but in Java, all casts are checked at runtime, and this check would always fail.

[Anton Uwe]

You would need to do a double casting like "C c= (C)(A)b;". The compiler would be happy then, but at runtime...

[Jesper de Jong]

Let's change the names of your classes a bit, then it will become more clear why this doesn't work.

Dog --- extends --> Animal
Cat --- extends --> Animal

If you have a Dog, can you cast it to a Cat - in other words, if you have a Dog, can you pretend that it's a Cat? No, you can't, because a Dog simply isn't a Cat.

(Remember that inheritance means "is a"; a Dog is an Animal, and a Cat is an Animal).