How can I create an event handling mechanism in Java? I'm used to ActiveX controls, which fire asynchronous events (i.e. when a control is finished a task, it notifies another component of that event).
The most common mechanism for this is the callback, where one class calls the method of another to notify it of an action or event. The class to be notified defines methods that will respond to specific events, such as when a mouse is clicked, dragged, or released. The AWT makes heavy use of this, with Listener interfaces. A class implements the event handling methods of a listener, and can then be registered with a component that generates these types of events. Classes that are event sources provide methods which register a listener, and at a later time when the event is generated, will invoke listener methods. The Abstract Windowing Toolkit (AWT) and Swing APIs would be a good place to start, to see if this suits your needs.