美国打官司费用:会JAVA的请进！！！！

import java.awt.*;
import java.awt.event.*;
public class TestMenuBar
{
MenuBar menubar = new MenuBar();
Menu fileM = new Menu("File");
Menu editM = new Menu("Edit");
Menu toolsM = new Menu("Tools");
Menu helpM = new Menu("Help");

MenuItem fileMI1 = new MenuItem("New");
MenuItem fileMI2 = new MenuItem("Open");
MenuItem fileMI3 = new MenuItem("Save");
CheckboxMenuItem fileMIb = new CheckboxMenuItem("Quit",true);

Menu filePrint = new Menu("print");
MenuItem printM1 = new MenuItem("preview");
MenuItem printM2 = new MenuItem("setting");

MenuListener m1 = new MenuListener();
printM1.addActionListener(m1);
// printM2.addActionListener(m1);
class MenuListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
if(e.getActionCommand().equals("preview"))
System.out.println("doing preview");
else if(e.getActionCommand().equals("setting"))
System.out.println("doing setting");
}
}

TestMenuBar()
{
FlowLayout f1 = new FlowLayout();

Frame f = new Frame("TestMenuBar");
f.setLayout(f1);

menubar.add(fileM);
menubar.add(editM);
menubar.add(toolsM);
menubar.add(helpM);

fileM.add(fileMI1);
fileM.add(fileMI2);
fileM.add(fileMI3);

filePrint.add(printM1);
filePrint.add(printM2);
fileM.add(filePrint);
fileM.addSeparator();
fileM.add(fileMIb);
f.setMenuBar(menubar);
f.setBounds(0,0,250,200);
f.setVisible(true);
f.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});

}
public static void main(String[] args)
{
new TestMenuBar();
}
}

请问这个问题改怎么解决，是什么原因，帮我分析一下，我给＋＋＋＋＋分！！！