《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.*;
				
				public class Test extends JApplet {
					private UndoableList list = new UndoableList();
					private JScrollPane scrollPane = new JScrollPane(list);
				
					private JButton addButton = new JButton("Add Item"),
									endButton = new JButton("End"),
									undoButton = new JButton("Undo");
				
					private UndoAction undoAction = new UndoAction();
					private CompoundEdit compoundEdit = new CompoundEdit();
					private int cnt=0;
				
					public void init() {
						Container contentPane = getContentPane();
				
						contentPane.setLayout(new FlowLayout());
						contentPane.add(addButton);
						contentPane.add(endButton);
						contentPane.add(undoButton);
						contentPane.add(scrollPane);
				
						scrollPane.setPreferredSize(new Dimension(150,150));
						list.addUndoableEditListener(undoAction);
				
						endButton.addActionListener(new ActionListener() {
							public void actionPerformed(ActionEvent e) {
								compoundEdit.end();
								updateButtonsEnabledState();
							}
						});
						addButton.addActionListener(new ActionListener() {
							public void actionPerformed(ActionEvent e) {
								list.undoableAdd("item #" + cnt++);
								updateButtonsEnabledState();
							}
						});
						undoButton.addActionListener(undoAction);
				
						endButton.setEnabled(false);
						undoButton.setEnabled(false);
					}
					private void updateButtonsEnabledState() {
						boolean inProgress = compoundEdit.isInProgress();
				
						endButton.setEnabled(inProgress);
						addButton.setEnabled(inProgress);
				
						if(undoButton.getText().equals("Undo"))
							undoButton.setEnabled(compoundEdit.canUndo());
						else
							undoButton.setEnabled(compoundEdit.canRedo());
					}
					class UndoAction extends AbstractAction 
									 implements UndoableEditListener {
				
						public UndoAction() {
							putValue(Action.NAME, "Undo");
						}
						public void actionPerformed(ActionEvent e) {
							String name = undoButton.getText();
							boolean isUndo = name.equals("Undo");
				
							if(isUndo) 	compoundEdit.undo();	
							else		compoundEdit.redo();	
				
							undoButton.setText(isUndo ? "Redo" : "Undo");
						}
						public void undoableEditHappened(UndoableEditEvent e) {
							UndoableEdit edit = e.getEdit();
							compoundEdit.addEdit(edit);
							endButton.setEnabled(true);
						}
					}
				}
				class UndoableList extends JList {
					UndoableEditSupport support = new UndoableEditSupport();
					DefaultListModel model;
				
					public UndoableList() {
						setModel(model = new DefaultListModel());
					}
					public void addUndoableEditListener(UndoableEditListener l) {
						support.addUndoableEditListener(l);
					}
					public void removeUndoableEditListener(
														UndoableEditListener l) {
						support.removeUndoableEditListener(l);
					}
					public void undoableAdd(Object s) {
						model.addElement(s);
						support.postEdit(new AddItemEdit());
					}
					class AddItemEdit extends AbstractUndoableEdit {
						Object lastItemAdded;
				
						public void undo() throws CannotUndoException {
							super.undo();
							lastItemAdded = model.getElementAt(model.getSize()-1);
							model.removeElement(lastItemAdded);
						}
						public void redo() throws CannotRedoException {
							super.redo();
							model.addElement(lastItemAdded);
						}
					}
				}