I don't think there is a way to access the owner of an object, I'm looking at the only possible package I know of that would allow this right now (java.lang.reflect) and I don't see anything. You could however get around this by passing the Field to the Ball in it's constructor or setting it via another Method, since Java uses pass by refrence for objects, you will be allowed to change the object there, if it's somewhere else just assign the object to a member object of the same type in the class, it'll still work.