Java equivalent of Cocoa delegates / Objective-C informal protocols?

Question

What is the Java equivalent of Cocoa delegates?

(I understand that I can have an interface passed to a class, and have that class call the appropriate methods, but I\'m

Answer 1

Best analog to an informal protocol I can think of is an interface that also has an adapter class to allow implementers to avoid implementing every method.

public class MyClass {

    private MyClassDelegate delegate;

    public MyClass () {

    }

    // do interesting stuff

    void setDelegate(MyClassDelegate delegate) {
        this.delegate = delegate;
    }

    interface MyClassDelegate {
        void aboutToDoSomethingAwesome();
        void didSomethingAwesome();
    }

    class MyClassDelegateAdapter implements MyClassDelegate {

        @Override
        public void aboutToDoSomethingAwesome() {
            /* do nothing */
        }

        @Override
        public void didSomethingAwesome() {
            /* do nothing */
        }
    }
}

Then someone can come along and just implement the stuff they care about:

class AwesomeDelegate extends MyClassDelegateAdapter {

    @Override
    public void didSomethingAwesome() {
        System.out.println("Yeah!");
    }
}

Either that, or pure reflection calling "known" methods. But that's insane.