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); } }