JAVA图形界面问题..（菜鸟级）

import java.awt.Button;
import java.awt.Frame;
import java.awt.Menu;
import java.awt.MenuBar;
import java.awt.MenuItem;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class LittleFrame extends Frame implements ActionListener {

private static final long serialVersionUID = 1L;
private MenuBar menuBar = new MenuBar();
private Menu menu = new Menu("菜单");
private MenuItem menuItem = new MenuItem("退出");
private Button button = new Button("退出");

public LittleFrame() {
super("LittleFrame");
setSize(100, 100);
setVisible(true);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});

this.setMenuBar(menuBar);
menuBar.add(menu)