collision detection

I had an idea for a project i could do, writing a 2d game framework.
I want to do collision detection and have a collision listener CollisionListener.
I only have a vague idea of how listeners work, and I have no experiance writing one, I've just used them.

Can someone explain the internal workings of listeners or give me a link to a page that does?

-Jonathan

Listeners are objects that sign on to another objects listener-list.
That object checks its listeners-list when events occur and informs the listenersof the event using a defined interface. Here is a simple example, note: this must be coded in three separate java-files...

Code:

---

/**
 * the interface used by the listener
 */
public interface BroadcastUser {
  public void changeWasMade (Object change);
}

/**
 * The class implementing the listener interface
 */
public class AnyClass implements BroadcastUser {
  protected Broadcaster bc=new Broadcaster();
  public AnyClass () {
    bc.addBroadCastUser(this);
  }
  public void changeWasMade (Object change) {
    System.out.println("Change reported:"+change.toString());
  }

}
/**
 * The class that reports to the listeners
 */
public class Broadcaster {
  ArrayList broadCastListeners=new ArrayList();
  public Broadcaster() {}
  // this class only recognizes its listeners as BroadcastUsers
  public void addBroadCastUser(BroadcastUser bu) {
    this.broadCastListeners.add(bu);
  }
  // in this method the change (or whatevver) is reported
  // to all the registered listeners
  public void aChangeMethod(Object aChange) {
    for (int i=0; i<boadCastListeners; i++) {
      BroadcastUser bu=(BroadcastUser)broadCastListeners.get(i);
      bu.changeWasMade(aChange);
    }
  }
}

---

Thank you.
I still have to write the collision detection and I was wondering if anyone has any suggestions about that.

Hint: you have to have a way of telling that two objects occupy the same area on the driveway at the same time, so you must have a driveway/area, and the location of each driver in that area at any time.