java Frame 控件变量要怎么使用

public FrameEventDemo() {

		getContentPane().setLayout(null);

		

		JLabel lbable = new JLabel("New label");

		lbable.setBounds(74, 51, 54, 15);

		getContentPane().add(lbable);



		setTitle("关闭提示");										

		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);			

		setBounds(100, 100, 450, 300);							

		contentPane = new JPanel();								

		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));

		setContentPane(contentPane);							

		contentPane.setLayout(null);

		

		JLabel lbNumber = new JLabel("New label");

		lbNumber.setBounds(75, 51, 54, 15);

		contentPane.add(lbNumber);

		

		

		addWindowListener(new WindowAdapter(){				

			@Override

			public void windowClosing(WindowEvent e){

				do_this_windowClosing(e);

			}

		});

		



		

		}

	protected void do_this_windowClosing(WindowEvent e){

		this.lbNumber.Text = "aaa";

	}