Well, there's three close-like methods:

    void close(Handler<AsyncResult<Void>> doneHandler)
    void close();

And:

    T closeHandler(Handler<Void> handler)

I think I'd leave this as is until the [bugzilla](https://bugs.eclipse.org/bugs/show_bug.cgi?id=423408) I created clarifies what is going on with these close methods. If there's any changes to promote them to a public interface, then I'd make further changes to adapt to that.