这个程序不能运行，请指教

你的JMenuBar对象add了自己，我在修改的地方添加了标记(//**)，修改如下，不懂得地方再发短消息给我：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class ActionSample extends JFrame
{
Action sampleAction;
Action exitAction;

public ActionSample()
{
super("Using Actions");

sampleAction=new AbstractAction()
{
public void actionPerformed(ActionEvent event)
{
JOptionPane.showMessageDialog(ActionSample.this,
                 "The SampleAction was invoked");
exitAction.setEnabled(true);
}
};
sampleAction.putValue(Action.NAME,"Sample Action");
sampleAction.putValue(Action.SMALL_ICON,new ImageIcon("help.gif"));
sampleAction.putValue(Action.SHORT_DESCRIPTION,"A Sample Action");
sampleAction.putValue(Action.MNEMONIC_KEY,new Integer('s'));

exitAction=new AbstractAction()
{
public void actionPerformed(ActionEvent event)
{
JOptionPane.showMessageDialog(ActionSample.this,
                   "The exitAction was invoked");
System.exit(0);
}
};
exitAction.putValue(Action.NAME,"Exit");
exitAction.putValue(Action.SMALL_ICON,new ImageIcon("exit.gif"));
exitAction.putValue(Action.SHORT_DESCRIPTION,"Exit Application");
exitAction.putValue(Action.MNEMONIC_KEY,new Integer('x'));
exitAction.setEnabled(false);

JMenu fileMenu=new JMenu("File");
fileMenu.add(sampleAction);
fileMenu.add(exitAction);
fileMenu.setMnemonic('F');

JMenuBar menuBar=new JMenuBar();
menuBar.add(fileMenu);
//menuBar.add(menuBar);  //**不可以自己添加自己，会抛出异常

JToolBar toolBar=new JToolBar();
toolBar.add(sampleAction);
toolBar.add(exitAction);

JButton sampleButton=new JButton();
sampleButton.setAction(sampleAction);

JButton exitButton=new JButton(exitAction);

JPanel buttonPanel=new JPanel();
buttonPanel.add(sampleButton);
buttonPanel.add(exitButton);

Container container=getContentPane();
container.add(toolBar,BorderLayout.NORTH);
container.add(buttonPanel,BorderLayout.CENTER);
}
public static void main(String[] args)
{
ActionSample sample=new ActionSample();
sample.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
sample.pack();
sample.setVisible(true);
}
}