Listener/Events

[Pho Tek]

Is there a name for this java idiom:
Class Listener{
foo( FooEvent f ) { ... } //1
bar( BarEvent b ) { ... } //2
}
I've also seen //1 and //2 collapsed into one method
and FooEvent & BarEvent moved into an inheritance hierachy.
Does this have any relation to "JavaBean event delegation", something I've heard thrown around in discussions ?
Also is this any similar to the Observer design pattern?
Pho

[Michael Ernest]

Hi Pho -
First let's call one out formally, so we can keep out terms clear:

public interface SomeListener extends java.util.EventListener
{
   public void someFoo(SomeEvent se);
   public void someBar(SomeEvent se);
}

where SomeEvent might then be defined:

public class SomeEvent extends java.util.EventListener
{
   public SomeEvent(Object eventSource) {
      super(eventSource);
   }
   ...
}

These are examples of a listener and event object in an event-delegation model, and their intent is functionally similar to Observer/Observable, so you're right on both counts.
------------------
Michael Ernest, co-author of: The Complete Java 2 Certification Study Guide