Ambiguous Polymorphism?

Question

In situations where two interfaces apply to an object, and there are two overloaded methods that differ only by distinguishing between those interfaces, which method gets called?

In code.

Click to copy

interface Foo {}
interface Bar {}

class Jaz implements Foo, Bar {}

void DoSomething(Foo theObject)
{
    System.out.println("Foo");
}

void DoSomething(Bar theObject)
{
    System.out.println("Bar");
}

Jaz j = new Jaz();
DoSomething(j);

Which method will get called? DoSomething(Foo) or DoSomething(Bar)? Neither is more specific than the other, and I see no reason why one should be called instead of the other, except that one is specified first/last.

EDIT: And with this type of code is it possible to force one or the other method?

Answer 1

This should be a compiler error.

This works:

Click to copy

DoSomething((Foo)j);
DoSomething((Bar)j);

Answer 2

I'm pretty sure the above won't compile. DoSomething(j) is an ambiguous call and will result in an error.

To get it to compile, you'd have to specifically cast j as a Foo or Bar when you call DoSomething, for example DoSomething((Foo)j).