Yeah, they are primarily like this indeed:

    void close(Handler<AsyncResult<Void>> doneHandler)
    void close();

There's already an interface called org.vertx.java.core.impl.Closeable, but only contains the first method, and it's only part of the implementation classes. IOW, none of the interfaces extend from it. 

I've created a [bugzilla](https://bugs.eclipse.org/bugs/show_bug.cgi?id=423408) to see if they can improve this on the java side.