How do I resolve ambiguous methods caused by intersection types in Java generics?

Question

I just recently discovered that you can specify multiple types in a single type parameter bound (see example). Like any new tool, I\'ve been trying to explore the possibilit

Answer 1

Note that the error is not related to generics, you get the same result if you use interfaces and a type is the intersection:

public class AA {

    interface XX{};
    interface YY{};

    public void doSomething(XX x){}
    public void doSomething(YY x){}

    class XY implements XX,YY{

    }

    public void runner(){
        doSomething(new XY());
    }
}

You get the same error in "doSomething", the compiler cannot resolve the ambiguity. Do you want to interpret as XX or as YY? You have to specify it with a cast. But if you have a hierarchy, like "YY extends XX" and "XY implements YY", the compiler can infer the correct method to call.