Question: The Observer pattern is used in the design of the J Button class, which has a method add Action Listener to let listeners register with the button so that they can be notified when the button is clicked. When such a click occurs, the J Button notifies all listeners by calling their action Performed methods. How are these two actions implemented? That is, what is in the body of the add ActionListener method, and how does the J Button go about notifying the listeners? To get a feeling for how this is done, create your own Publisher class with an add Subscriber method and a broadcast method and create a Subscriber class with a something Happened method. The Publisher's broadcast method should call all the something Happened methods of the Subscribers.