learning java AWT MenuBar Menu MenuItem菜单

import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class SimpleMenu {
    private Frame f  = new Frame("test");
    private MenuBar mb = new MenuBar();
    Menu file  =  new Menu("file");
    Menu edit  =  new Menu("edit");

    MenuItem crateItem = new MenuItem("create");
    MenuItem saveItem = new MenuItem("save");

    MenuItem exitItem = new MenuItem("exit",
            new MenuShortcut(KeyEvent.VK_X));

    CheckboxMenuItem autoWrap = new CheckboxMenuItem("autoWrap");

    MenuItem copyItem = new MenuItem("copy");
    MenuItem pasteItem = new MenuItem("paste");

    Menu format =  new Menu("format");
    /*ctrl + shift + / */
    MenuItem commentItem = new MenuItem("comment", new MenuShortcut(KeyEvent.VK_SLASH,true));

    MenuItem cancelItem = new MenuItem("cancelComment");
    private TextArea ta = new TextArea(6,40);

    public void init(){
        ActionListener menuListener = e -> {
          var cmd = e.getActionCommand();
          ta.append(" click " + cmd + " menu " + " 
 ");
          if(cmd.equals("exit")){
              System.exit(0);
          }
        };

        commentItem.addActionListener(menuListener);
        exitItem.addActionListener(menuListener);

        file.add(crateItem);
        file.add(saveItem);
        file.add(exitItem);

        edit.add(autoWrap);
        edit.addSeparator();
        edit.add(copyItem);
        edit.add(pasteItem);

        format.add(commentItem);
        format.add(cancelItem);

        edit.add(new MenuItem("-"));
        edit.add(format);



        mb.add(file);
        mb.add(edit);
        f.setMenuBar(mb);
        f.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });

        f.add(ta);
        f.pack();
        f.setVisible(true);

    }

    public static void main(String[] args) {
        new SimpleMenu().init();
    }


}

output: