Hvorledes tilføjes undermenuer til Jmenu

Du opretter JMenuItems og add'er dem til din JMenuBar

kig evt. lidt på det her:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class TestKlasseSwing extends JFrame implements WindowListener
{
    private int frameWidth = 640;
    private int frameHeight = 480;
    private JMenuBar jmb;
    private JMenu jm1;
    private JMenu jm2;
    private JMenuItem jmi1;
    private JMenuItem jmi2;

    public TestKlasseSwing()
    {
        createFrame();
    }

    private void createFrame()
    {
        setTitle("TestKlasseSwing");
        setResizable(false);
        addWindowListener(this);           
        //Place components here:
       
        jmi1 = new JMenuItem("MenuItem1");
        jmi2 = new JMenuItem("MenuItem2");
        jm1 = new JMenu("Test");       
        jm2 = new JMenu("Test");
        jm1.add(jmi1);
        jm1.add(jm2);
        jm2.add(jmi2);
       
        jmb = new JMenuBar();
        jmb.add(jm1);
        this.getContentPane().add(jmb, BorderLayout.NORTH);
       
        //Center Frame
        java.awt.Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
        setSize(new java.awt.Dimension(frameWidth, frameHeight));
        setLocation( (screenSize.width-this.getWidth()) / 2, (screenSize.height - this.getHeight()) / 2);
    }

    public void windowOpened(WindowEvent e){}
    public void windowClosing(WindowEvent e){ dispose(); System.exit(0);}
    public void windowClosed(WindowEvent e){}
    public void windowIconified(WindowEvent e){}
    public void windowDeiconified(WindowEvent e){}
    public void windowActivated(WindowEvent e){}
    public void windowDeactivated(WindowEvent e){}
}

class Main
{
    public static void main(String args[])
    {
          new TestKlasseSwing().show();
    }
}

Og hvis du vil have undermenuer add´er du en JMenu til en anden JMenu..

MenuPunkt = new JMenuItem("Menupunkt");
Menu = new JMenu("Menu");       
Undermenu = new JMenu("Undermenu");
Undermenu.add(MenuPunkt);
Menu.add(Undermenu);

menuBar = new JMenuBar();
menuBar.add(Menu);

private javax.swing.JMenu jMenu1;
    private javax.swing.ButtonGroup buttonGroup2;
    private javax.swing.ButtonGroup buttonGroup1;
    private javax.swing.JMenuItem jMenuItem2;
    private javax.swing.JMenuItem jMenuItem1;



private void initComponents() {
       
        jMenuBar1 = new javax.swing.JMenuBar();
        jMenu1 = new javax.swing.JMenu();
        jMenuItem1 = new javax.swing.JMenuItem();
        jMenuItem2 = new javax.swing.JMenuItem();

     
        jMenu1.setText("Menu");
        jMenuItem1.setText("Item");
        jMenu1.add(jMenuItem1);
        jMenuItem2.setText("Item");
        jMenu1.add(jMenuItem2);
        jMenuBar1.add(jMenu1);
        setJMenuBar(jMenuBar1);

  }