《Java2图形设计卷II：Swing》配套光盘源码

				import javax.swing.*;
				import javax.swing.event.*;
				import javax.swing.undo.*;
				import java.awt.*;
				import java.awt.event.*;
				import java.util.*;
				
				public class Test extends JApplet {
					private TextFieldPanel panel = new TextFieldPanel();
					private StateEdit stateEdit;
				
					private JButton startButton = new JButton("Start Edit"),
									endButton = new JButton("End Edit"),
									undoButton = new JButton("Undo");
				
					public void init() {
						Container contentPane = getContentPane();
				
						contentPane.setLayout(new FlowLayout());
						contentPane.add(startButton);
						contentPane.add(endButton);
						contentPane.add(undoButton);
						contentPane.add(panel);
				
						endButton.setEnabled(false);
						undoButton.setEnabled(false);
				
						startButton.addActionListener(new ActionListener() {
							public void actionPerformed(ActionEvent e) {
								stateEdit = new StateEdit(panel);
								endButton.setEnabled(true);
								startButton.setEnabled(false);
							}
						});
						endButton.addActionListener(new ActionListener() {
							public void actionPerformed(ActionEvent e) {
								stateEdit.end();
								undoButton.setEnabled(true);
								endButton.setEnabled(false);
							}
						});
						undoButton.addActionListener(new ActionListener() {
							public void actionPerformed(ActionEvent e) {
								String name = undoButton.getText();
								boolean isUndo = name.equals("Undo");
				
								if(isUndo) 	stateEdit.undo();	
								else		stateEdit.redo();	
				
								undoButton.setText(isUndo ? "Redo" : "Undo");
							}
						});
					}
				}
				class TextFieldPanel extends JPanel implements StateEditable {
					JTextField[] fields = new JTextField[] {
						new JTextField("text field 1"), 
						new JTextField("text field 2"),
						new JTextField("text field 3"), 
						new JTextField("text field 4"),
					};
				
					public TextFieldPanel() {
						setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
				
						for(int i=0; i < fields.length; ++i)
							add(fields[i]);
					}
					public void storeState(Hashtable hashtable) {
						for(int i=0; i < fields.length; ++i)
							hashtable.put(fields[i], fields[i].getText());
					}
					public void restoreState(Hashtable hashtable) {
						Enumeration keys = hashtable.keys();
				
						while(keys.hasMoreElements()) {
							JTextField field = (JTextField)keys.nextElement();
							field.setText((String)hashtable.get(field));
						}
					}
				}