像toribash的游戏:java问题，工具用的是Netbeans,不知道怎么改。

package lilinhao;
import java.awt.*;
import java.awt.event.*;

public class MenuTest implements ActionListener{
Frame fr;

public static void main(String args[]) {
MenuTest mt=new MenuTest();
mt.go();
}
public void go(){
fr=new Frame("MenuTest");
MenuBar mb=new MenuBar();
Menu m1=new Menu("File");
Menu m2=new Menu("Edit");
Menu m3=new Menu("Help");
mb.add(mi1);
mb.add(mi2);
mb.setHelpMenu(m3);
Menultem mi1=new Menultem("save");
Menultem mi2=new Menultem("Open");
Menultem mi3=new Menultem("exit");
m1.add(mi1);
m1.add(mi2);
m1.Separator();
m1.add(mi3);
mi3.addActionListener(this);
fr.setSize(300, 200);
fr.setVisble(true);
}
public void actionPerformed(ActionEvent e){
System.exit(0);
}

}