一个简单的笔记本小程序，熟悉了JTree和DefaultMutableTreeNode类的使用。
程序运行结果图：
代码：
import java.awt.BorderLayout;import java.awt.Container;import java.awt.TextArea;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileNotFoundException;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;import javax.swing.JScrollPane;import javax.swing.JSplitPane;import javax.swing.JTree;import javax.swing.UIManager;import javax.swing.UnsupportedLookAndFeelException;import javax.swing.event.TreeSelectionEvent;import javax.swing.event.TreeSelectionListener;import javax.swing.tree.DefaultMutableTreeNode;public class Diary extends JFrame implements ActionListener, TreeSelectionListener { public static void main(String[] args) { try { UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel"); //SwingUtilities.updateComponentTreeUI(this); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InstantiationException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (UnsupportedLookAndFeelException e) { // TODO Auto-generated catch block e.printStackTrace(); } new Diary(); } JTree tree = null; DefaultMutableTreeNode root = null; TextArea text = new TextArea(20, 20); JButton b_save = new JButton("保存日志"); JButton b_delete = new JButton("删除日志"); JPanel p = new JPanel(); JPanel p1 = new JPanel(); JLabel l = new JLabel(" "); JScrollPane sp; Container c = this.getContentPane(); DefaultMutableTreeNode[] month = new DefaultMutableTreeNode[13]; Diary() { root = new DefaultMutableTreeNode("日历记事本"); for (int i = 1; i <= 12; i++) { month[i] = new DefaultMutableTreeNode(i + "月"); root.add(month[i]); } for (int i = 1; i <= 12; i++) { if (i == 1 | i == 3 | i == 5 | i == 7 | i == 8 | i == 10 | i == 12) { for (int j = 1; j <= 31; j++) { month[i].add(new DefaultMutableTreeNode(j + "日")); } } else if (i == 4 | i == 6 | i == 9 | i == 11) { for (int j = 1; j <= 30; j++) { month[i].add(new DefaultMutableTreeNode(j + "日")); } } else { for (int j = 1; j <= 28; j++) { month[i].add(new DefaultMutableTreeNode(j + "日")); } } } tree = new JTree(root); p.setLayout(new BorderLayout()); sp = new JScrollPane(tree); tree.addTreeSelectionListener(this); p1.add(b_save); p1.add(b_delete); b_save.addActionListener(this); b_delete.addActionListener(this); p.add(p1, BorderLayout.NORTH); p.add(text, BorderLayout.CENTER); p.add(l, BorderLayout.SOUTH); JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, true, sp, p); this.add(splitPane); this.setTitle("Diary"); this.setBounds(400, 300, 460, 320); this.setVisible(true); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } @Override public void valueChanged(TreeSelectionEvent e) { // TODO Auto-generated method stub text.setText(null); if (e.getSource() == tree) { DefaultMutableTreeNode node = (DefaultMutableTreeNode) tree .getLastSelectedPathComponent(); try { if (node.isLeaf()) { String str = node.toString(); for (int i = 1; i <= 12; i++) { if (node.getParent() == month[i]) { String temp = null; File f = new File(node.getParent().toString() + str + ".txt"); try { FileReader fr = new FileReader(f); BufferedReader br = new BufferedReader(fr); while ((temp = br.readLine()) != null) { text.append(temp + '\n'); } br.close(); fr.close(); } catch (FileNotFoundException e1) { } catch (Exception e1) { e1.printStackTrace(); } } } } } catch (NullPointerException e1) { } } } @Override public void actionPerformed(ActionEvent e) { // TODO Auto-generated method stub DefaultMutableTreeNode node = (DefaultMutableTreeNode) tree .getLastSelectedPathComponent(); if (e.getSource() == b_save) { try { if (node.isLeaf()) { String str = node.toString(); File f = new File(node.getParent().toString() + str + ".txt"); try { FileWriter fw = new FileWriter(f); BufferedWriter bw = new BufferedWriter(fw); bw.write(text.getText(), 0, text.getText().length()); bw.flush(); bw.close(); fw.close(); } catch (IOException e1) { e1.printStackTrace(); } l.setText("日志已保存"); new Thread(new Disappear()).start(); } } catch (NullPointerException e1) { l.setText("请选择日期"); new Thread(new Disappear()).start(); } } else if (e.getSource() == b_delete) { try { if (node.isLeaf()) { String str = node.toString(); File f = new File(node.getParent().toString() + str + ".txt"); f.delete(); text.setText(null); l.setText("日志已删除"); new Thread(new Disappear()).start(); } } catch (NullPointerException e1) { l.setText("请选择日志"); new Thread(new Disappear()).start(); } } } class Disappear implements Runnable { @Override public void run() { // TODO Auto-generated method stub try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } l.setText(" "); } }}