code: public void addActionComponent( JComponent item )
    {
      if( !SwingUtilities.isEventDispatchThread() )
      {
        throw new RuntimeException( "Whoops!  UpdateNotifier is restricted to the EventDispatch thread." );
      }
      _mapItems.put( item, null );
    }
docs: Adds a component to the enable/disable map.
  
  @param item A component for which the class controls the enable state.