/**
     * Invoked when the user attempts to close the window
     * from the window's system menu.  If the program does not 
     * explicitly hide or dispose the window while processing 
     * this event, the window close operation will be cancelled.
     */
     public   void  windowClosing(WindowEvent e);

    /**
     * Adds the specified window listener to receive window events from
     * this window.
     * If l is null, no exception is thrown and no action is performed.
     *
     * @param 	l the window listener
     * @see #removeWindowListener
     * @see #getWindowListeners
     */ 
     public   synchronized   void  addWindowListener(WindowListener l) {