[Mac App] A simple Menu Bar App in Java

import java.awt.AWTException;
import java.awt.Image;
import java.awt.MenuItem;
import java.awt.PopupMenu;
import java.awt.SystemTray;
import java.awt.Toolkit;
import java.awt.TrayIcon;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.MalformedURLException;
import java.net.URL;

public class MenuBarIconTest {
    public static void main(String[] args) throws MalformedURLException {
        TrayIcon trayIcon = null;
         if (SystemTray.isSupported()) {
             // get the SystemTray instance
             SystemTray tray = SystemTray.getSystemTray();
             // load an image
             Image image = Toolkit.getDefaultToolkit().getImage(new URL("http://cdn1.iconfinder.com/data/icons/Hypic_Icon_Pack_by_shlyapnikova/16/forum_16.png"));
             // create a action listener to listen for default action executed on the tray icon
             ActionListener listener = new ActionListener() {
                 public void actionPerformed(ActionEvent e) {
                     System.out.println("action");
                     // execute default action of the application
                     // ...
                 }
             };
             // create a popup menu
             PopupMenu popup = new PopupMenu();
             // create menu item for the default action
             MenuItem defaultItem = new MenuItem("Do the action");
             defaultItem.addActionListener(listener);
             popup.add(defaultItem);
             /// ... add other items
             // construct a TrayIcon
             trayIcon = new TrayIcon(image, "Tray Demo", popup);
             // set the TrayIcon properties
             trayIcon.addActionListener(listener);
             // ...
             // add the tray image
             try {
                 tray.add(trayIcon);
             } catch (AWTException e) {
                 System.err.println(e);
             }
             // ...
         } else {
             // disable tray option in your application or
             // perform other actions
             //...
         }
         // ...
         // some time later
         // the application state has changed - update the image
         if (trayIcon != null) {
             //trayIcon.setImage(updatedImage);
         }

    }
}

reference:

https://stackoverflow.com/questions/13481504/creating-an-nsstatusitem-menubar-app-in-java