7. 如何用JAVA编写“记事本”程序 import java.io.*;import java.util.Calendar;import java.awt.*;import java.awt.event.*;import javax.swing.*;public class NoteBook extends JFrame implements ActionListener,ItemListener,WindowListener,MouseListener{ Container c = this.getContentPane(); JMenuBar jmb = new JMenuBar(); JColorChooser jcc = new JColorChooser(); JMenu jm1 = new JMenu（"文件（F）"); JMenu jm2 = new JMenu（"编辑（E）"); JMenu jm3 = new JMenu（"格式（O）"); JMenu jm4 = new JMenu（"查看（V）"); JMenu jm5 = new JMenu（"帮助（H）"); JMenuItem jmi1 = new JMenuItem（"新建（N）"); JMenuItem jmi2 = new JMenuItem（"打开（O）"); JMenuItem jmi3 = new JMenuItem（"保存（S）"); JMenuItem jmi4 = new JMenuItem（"退出（X）"); JMenuItem jmi5 = new JMenuItem（"撤消（U）"); JMenuItem jmi6 = new JMenuItem（"复制（C）"); JMenuItem jmi7 = new JMenuItem（"粘贴（P）"); JMenuItem jmi8 = new JMenuItem（"剪切（T）"); JMenuItem jmi12 = new JMenuItem（"日期和时间"）； JMenuItem jmi9 = new JMenuItem（"字体（E）"); JCheckBoxMenuItem jcbmi = new JCheckBoxMenuItem（"自动换行（W）"); JMenuItem jmi10 = new JMenuItem（"删除（S）"); JMenuItem jmi11 = new JMenuItem（"背景颜色（H）"); JTextArea jta = new JTextArea(15,15); JScrollPane jsp = new JScrollPane(jta); //PupolMenu pm = new Pupolmenu(); NoteBook(){ this.addWindowListener(this); c.setLayout(new BorderLayout()); c.add(jmb,BorderLayout.NORTH); this.setTitle（"新建 文本文档"）； jmb.add(jm1); jm1.setMnemonic('f'); jm1.addActionListener(this); jmb.add(jm2); jm2.setMnemonic('e'); jmb.add(jm3); jm3.setMnemonic('o'); jmb.add(jm4); jm4.setMnemonic('v'); jmb.add(jm5); jm5.setMnemonic('h'); jm1.add(jmi1); jmi1.addActionListener(this); jmi1.setAccelerator(KeyStroke.getKeyStroke('N',Event.CTRL_MASK,false)); jm1.addSeparator(); jm1.add(jmi2); jmi2.setAccelerator(KeyStroke.getKeyStroke('O',Event.CTRL_MASK,false)); jmi2.addActionListener(this); jm1.addSeparator(); jm1.add(jmi3); jmi3.setAccelerator(KeyStroke.getKeyStroke('S',Event.CTRL_MASK,false)); jmi3.addActionListener(this); jm1.addSeparator(); jm1.add(jmi4); jmi1.setMnemonic('n'); jmi2.setMnemonic('o'); jmi3.setMnemonic('s'); jmi4.setMnemonic('x'); jmi4.addActionListener(this); jm2.add(jmi5); jm2.addSeparator(); jm2.add(jmi6); jm2.addSeparator(); jm2.add(jmi7); jm2.addSeparator(); jm2.add(jmi8); jm2.add(jmi12); jmi12.addActionListener(this); jm3.add(jcbmi); jcbmi.addItemListener(this); jm3.addSeparator(); jm3.add(jmi9); jm4.add(jmi10); jmi10.addActionListener(this); jm5.add(jmi11); jmi11.addActionListener(this); c.add(jsp); this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); this.setSize(500,500); this.setVisible(true); } public void actionPerformed(ActionEvent e){ if(e.getSource()==jmi1){ jta.setText(""); this.setTitle（"无标题 - 记事本"）； } if(e.getSource()==jmi2){ File f1; JFileChooser jfc1 = new JFileChooser(); int num1 = jfc1.showOpenDialog(this); if(num1==JFileChooser.APPROVE_OPTION){ try{ f1 = jfc1.getSelectedFile(); this.setTitle(f1.getName()); FileReader fr = new FileReader(f1); BufferedReader br = new BufferedReader(fr); String str; while((str = br.readLine())!=null){ jta.setText(str); } fr.close(); br.close(); }catch(FileNotFoundException e1){ e1.printStackTrace(); }catch(IOException e2){ e2.printStackTrace(); } } } if(e.getSource()==jmi3){ File f2 = null; JFileChooser jfc2 = new JFileChooser(); int num2 = jfc2.showSaveDialog(this); if(num2==JFileChooser.APPROVE_OPTION){ f2=jfc2.getSelectedFile(); this.setTitle(f2.getName()); try{ FileWriter fw = new FileWriter(f2); BufferedWriter bw = new BufferedWriter(fw); bw.write(jta.getText()); bw.close(); fw.close(); }catch(IOException e2){ e2.printStackTrace(); } } } if(e.getSource()==jmi4){ int a = JOptionPane.showConfirmDialog(this，"文件已被改变，是否要保存？"，"提示"，JOptionPane.YES_NO_CANCEL_OPTION); if(a==1){ this.dispose(); }else if(a==0){ File f2 = null; JFileChooser jfc2 = new JFileChooser(); int num2 = jfc2.showSaveDialog(this); if(num2==JFileChooser.APPROVE_OPTION){ f2=jfc2.getSelectedFile(); this.setTitle(f2.getName()); try{ FileWriter fw = new FileWriter(f2); BufferedWriter bw = new BufferedWriter(fw); bw.write(jta.getText()); bw.close(); fw.close(); }catch(IOException e2){ e2.printStackTrace(); } this.dispose(); } } } if(e.getSource()==jmi12){ Calendar c1 =Calendar.getInstance(); int y = c1.get(Calendar.YEAR); int m = c1.get(Calendar.MONTH); int d = c1.get(Calendar.DATE); int h = c1.get(Calendar.HOUR); int m1 = c1.get(Calendar.MINUTE); int m2 = m+1; jta.setText(y+"年"+m2+"月"+d+"日"+h+":"+m1); } if(e.getS 。