Interface cast to final class

Question

Read in a book saying that an interface object cannot be cast to a final class object. See the following:
final class Apple { }
interface Squeezable{ }
class Citrus implements Squeezable{ }In this case then:
Squeezable sq = new Citrus();
Apple apple = (Apple)sq; // compile errorOf course there are two fixes for the compile error.
(1) Make Apple implement Squeezable (this is easy to understand).
(2) Make Apple a non-final class (although there will be a runtime exception).
Can anybody tell me why it won't compile when Apple is a final class? What's going on behind the scene with the compiler here? Thanks!

Answer 1

senore100 wrote:
Thanks for all your reply. Well, actually the compiler should know that the actual object is a Citrus. No, it shouldn't. It doesn't become a Citrus obejct until runtime. The compiler only looks at the reference type on the left side of the =, not what's happening on the right side.
What if instead of new, it was Squeezeable sq = squeezableFactory.createSqueezeable(); It could return any class that implements Squeezeable.
Now, you could try to argue that it should at least do it for new, when it knows what the class will be. But there's really no point for that, and it would just complicate the language by adding special cases.