java program example to update menu on the fly

JL.java

import javax.swing.*;

public class JL {

    JFrame f = null;
    JMenuBar mb = null;
    JMenu fm = null;
    JMenuItem mi = null;

    private void sleep() {
        try { Thread.sleep(1000); } catch(Exception e) {}
    }

    private void make_background_thread() {
        Runnable r = new Runnable() { // make a runnable
            public void run() {
                while(true) {   // infinite loop here
                    sleep();    // wait a second
                    if (fm!=null) { // if the file menu has been created

                        // odd java syntax here, create another runnable
                        // for the swing invoke later
                        SwingUtilities.invokeLater(
                            new Runnable() {
                                public void run() {
                                    // fm is not null this is safe
                                    fm.setText("file:" + System.currentTimeMillis());
                                }
                            }
                        );
                    }
                }
            }
        };

        // create the background thread
        Thread t = new Thread(r);

        // run forest run
        t.start();
    }
    public void start() {

        make_background_thread();

        f = new JFrame("JL");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        mb = new JMenuBar();
        fm = new JMenu("File");
        mb.add(fm);
        mi = new JMenuItem("woohoo");
        fm.add(mi);

        f.setJMenuBar(mb);
        f.setSize(200,200);
        f.setVisible(true);
    }

    public static void main(String [] args) {
        JL mainline = new JL();
        mainline.start();
    }
}