generic question

[zheng li]

class B<E> {}
class GenClass<E extends B> {
    public <T extends E> B<? super T> getNow(B<? super T> a) {
        return new B();    // compilation successes
        return new E();    // compilation fails
    }
}

why?

how could i return E?

[Horia Constantin]

Well, I can say from start that that code will never compile because you cannot have 2 returns like that (one after another). It will not compile (and probably say statement unreachable).

The question that arises... Didn't you check the error given by the compiler at compile time? That should have been pretty obvious.

Next time pay more attention to what the compiler has to say (questions like these are to be expected at the exam).

Cheers,
Horia

[Allan Cheong]

I don't think you can return E. E is a generic type. You can only return an object of type reference B.

[Ankit Garg]

Yes E is a generic type. At runtime, it actually doesn't denotes anything, so you can't instantiate an object of type E. You'll have to create an instance of an actual type (class or interface) that is compatible with E. Since here E here is <E extends B>, so you can return an instance of B or a subclass of B...

[zheng li]

Ankit Garg wrote:Yes E is a generic type. At runtime, it actually doesn't denotes anything, so you can't instantiate an object of type E. You'll have to create an instance of an actual type (class or interface) that is compatible with E. Since here E here is <E extends B>, so you can return an instance of B or a subclass of B...

thank you