code: private ArrayList getListener()
      {
          if (_listeners != null)
              return _listeners;
          synchronized (this) {
              if (_listeners != null)
                  return _listeners;
              _listeners = new ArrayList();
          }
          return _listeners;
      }
docs: This method will return the event listener <code>ArrayList</code> when called.  The event listener is
  lazily created.
  @return The listener array list.