本题中，在窗口右侧添加了一个菜单，右侧为一个文本域，菜单有“File”和“Help”，“File”菜单中有菜单项“New”、“Open”、“Save”、“Save as”和“Exit”，其中“Open”的快捷键为＜Ctrl+O＞，“Save”的快捷键为＜Ctrl+S＞，而“Help”菜单以及其中的菜单项“Index”和“About”没定了第一个字母为其快捷字母，通过鼠标单击任一个菜单项或通过快捷键以及快捷字母，都能在后台输入所选择的菜单项。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class java2 extends JFrame______
private JMenuItem saveItem;
private JMenuItem saveAsItem;
private JPopupMenu popup;
private JTextArea textArea;
public java2()
setTitle("java2");
setSize(400,300);
addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent e)
System.exit(0);
);
textArea=new JTextArea(0,0);
Container contentPane=getContentPane();
contentPane.add(new JScrollPane(textArea),"Center");
JMenuBar menuBar=new JMenuBar();
menuBar.setLayout(new BoxLayout(menuBar,BoxLayout.Y_AXIS));
getContentPane().add(menuBar,BorderLayout.WEST);
HorizontalMenu fileMenu=new HorizontalMenu("File");
fileMenu.addMenuListener(this);
JMenuItem openItem=new JMenuItem("Open");
openItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_0,InputEvent.CTRL_MASK));
saveItem=new JMenuItem("Save");
saveItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S,InputEvent.CTRL_MASK));
saveAsItem=new JMenuItem("Save As");
menuBar.add(makeMenu(fileMenu,
new Object[]
"New",openItem,null,saveItem,saveAsItem,null,"Exit"
,this));
HorizontalMenu helpMenu=new HorizontalMenu("Help");
helpMenu.______(’H’);
menuBar.add(Box.createVerticalGlue());
menuBar.add(makeMenu(helpMenu,
new Object[]
new JMenuItem("Index",’I’),
new JMenuItem("About",’A’)
,this));
public void actionPerformed(ActionEvent evt)
String arg=evt.getActionCommand();
System.out.println(arg);
if(arg.equals("Exit"))
System.exit(0);
public void menuSelected(MenuEvent evt)
public void menuDeselected(MenuEvent evt)
public void menuCanceled(MenuEvent evt)
public HorizontalMenu makeMenu(Object parent,Object[]items,Object target)
HorizontalMenu m=null;
if(parent instanceof HorizontalMenu)
m=(HorizontalMenu)parent;
else if(parent instanceof String)
m=new HorizontalMenu((String)parent);
else
return null;
m.setMinimumSize(m.getPrefeHedSize());
for(int i=0;i＜items.length;i++)
if(items[i]==null)
m.addSeparator();
else
m.add(makeMenuItem(items[i],target));
return m;
public static JMenuItem makeMenuItem(Object item,Object target)
JMenuItem r=null;
if(item instanceof String)
r=new JMenuItem((String)item);
else if(item instanceof JMenuItem)
r=(JMenuItem)item;
else return null;
if(target instanceof ActionListener)
r.addActionListener((ActionListener)target);
return r;
class HorizontalMenu extends JMenu
HorizontalMenu(String label)
super(label);
JPopupMenu pm=getPopupMenu();
pm.setLayout(new BoxLayout(pm,BoxLayout.X_AXIS));
setMinimumSize(getPreferredSize());
public static void main(string[]args)
Frame f=new java2();
f.show();