javax.swing.SwingUtilities.invokeLater(function() {
  var frame = new Packages.javax.swing.JFrame();
  frame.defaultCloseOperation = javax.swing.JFrame.EXIT_ON_CLOSE;

  var menuBar = new Packages.javax.swing.JMenuBar();
  frame.setJMenuBar(menuBar);

  var fileMenu = new Packages.javax.swing.JMenu("File");
  menuBar.add(fileMenu);

  importClass(Packages.javax.swing.JMenuItem);

  var openItem = new JMenuItem("Open...");
  openItem.addActionListener(function() {
      print("put your file open code here!\n");
  });
  fileMenu.add(openItem);

  fileMenu.add(new Packages.javax.swing.JSeparator());

  var quitItem = new JMenuItem("Quit");
  quitItem.addActionListener(function() {
      java.lang.System.exit(0);
  });
  fileMenu.add(quitItem);

  frame.setSize(640, 480);
  frame.visible = true;
});

// Park the main thread.  Otherwise the application would immediately exit.
java.util.concurrent.locks.LockSupport.park();

A simple example of creating a Swing application using the JavaScript support provided by the Scripting API.

JavaScript Swing Application

JavaScript