Question

How can I cast two extends class like that in java?

    class B extends Object{

    }

    class C extends Object{

    }

    B b = new B();

    C c = (C)b;//Cannot cast from B to C

Answer 1

You can’t. Consider a slight rename:

class Ford extends Car {

}
class Chevrolet extends Car {

}

Ford ford = new Ford();

Chevrolet chevrolet = (Chevrolet) ford;

Both are, however, a Car so you can say

Car car = ford;

but not any more than that.