java 编写的 记事本

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class JNotePadUI extends JFrame {
private JMenuItem menuOpen;
private JMenuItem menuSave;
private JMenuItem menuSaveAs;
private JMenuItem menuClose;

private JMenu editMenu;
private JMenuItem menuCut;
private JMenuItem menuCopy;
private JMenuItem menuPaste;

private JMenuItem menuAbout;

private JTextArea textArea;
private JLabel stateBar;
private JFileChooser fileChooser;

private JPopupMenu popUpMenu;

public JNotePadUI() {
super("新建文本文件");
setUpUIComponent();
setUpEventListener();
setVisible(true);
}

private void setUpUIComponent() {
setSize(640, 480);

// 菜单栏
JMenuBar menuBar = new JMenuBar();

// 设置「文件」菜单
JMenu fileMenu = new JMenu("文件");
menuOpen = new JMenuItem("