Dynamically populating a JMenu

Question

I'm new to Java, but was hoping someone could point me in the right direction for populating a menu with items as it is about to be displayed. This would be a cascading menu off a JMenu off a JMenuBar. I have figured out how to populate the JMenu, but don't know which hook to use to get notification that the user is about to display the cascading menu.

Answer 1

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.util.Random;
public class Test extends JFrame {
  String[] nums = {"One","Two","Three","Four","Five","Six"};
  JMenu jm = new JMenu("Menu");
  Random r = new Random();
  public Test() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container content = getContentPane();
    JMenuBar jmb = new JMenuBar();
    setJMenuBar(jmb);
    jmb.add(jm);
    jm.addMenuListener(new MenuListener() {
      public void menuSelected(MenuEvent me) {
        jm.removeAll();
        for (int i=0; i<5; i++) {
          jm.add(new JMenuItem(nums[r.nextInt(nums.length)]));
      public void menuDeselected(MenuEvent me) {}
      public void menuCanceled(MenuEvent me) {}
    setSize(200, 200);
    setVisible(true);
  public static void main(String[] args) { new Test(); }
}