Action X Observer

/**
 * Define an interface for Connection listeners
 */
public interface ConnectionListener extends EventListener
{
   /**
    * Informs the stopping of the connection.
    * @param evt The ConnectionEvent that describes the problem.
    */
   void connectionStopped(ConnectionEvent evt);
   
   /**
    * Informs that the connection was opened.
    * @param evt The ConnectionEvent describing the opening. 
    */   
   void connectionOpened(ConnectionEvent evt);
}

/**
 * Represent any events generated by the <tt>Connection</tt> object.
 * @author Vendramin, Márcio
 * @author Mendonça, Vinícius Godoy de
 */
public class ConnectionEvent extends EventObject
{   
   /**Create a new connection event
    * @param source The connection that generated the event.
    */
   public ConnectionEvent(Object source)
   {      
      super(source);
   }
}

List<ConnectionListener> listeners = new ArrayList<ConnectionListener();

public void add(ConnectionListener listener) {
   if (listener == null) 
     throw new NullPointerException("Listener cannot be null!");
   listeners.add(listener);
}

public void remove(ConnectionListener listener) {
   listeners.remove(listener);
}

public void fireConnectionOppened() {
     ConnectionEvent evt = new ConnectionEvent(this);
     for (Listener l : listeners) {
          l.connectionOpened(evt);
     }
}

public void fireConnectionStopped() {
     ConnectionEvent evt = new ConnectionEvent(this);
     for (Listener l : listeners) {
          l.connectionStopped(evt);
     }
}