Is it possible to make type safe Java Collections whose members merely implement several interfaces?

Question

If I have:

interface A{  void a();  }
interface B{  void b();  }

I can hava a generic method like this:

class C {
    <T extends A & B> void c(T t) {
        t.a();
        t.b();
    }
}

But i can't hava a generic collection like this:

class D{
    List<? extends A & B> l;
}

I know that I could make an empty interface E that extends both A and B, and have a List that contains E's... but I'd rather leave my classes marked with just A and B, and not have to have an E. This is even more problematic when there are many more A's and B's that can be combined in 2^n ways.

I would rather be able to define a type on the fly, as a union of interfaces, and have the collections recognize objects that implement all of the interfaces as instances of that type.

Is there a way to do this in Java? I'm open to any kind of work around or hack at this point in order to avoid making a new interface, and tagging my classes with it, just so that they can live together in a collection. Or, if someone could clarify for me why this is impossible, that would be equally appreciated.

Answer 1

public class Foo<T extends A & B> {
    private List<T> list;
    //getters, setters, etc.
}