Fill a menu dynamically when menu is shown

[Java Tip]

import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.MenuItem;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Tree;
import org.eclipse.swt.widgets.TreeItem;

public class Snippet97 {

  public static void main(String[] args) {
    final Display display = new Display();
    Shell shell = new Shell(display);
    final Tree tree = new Tree(shell, SWT.BORDER | SWT.MULTI);
    final Menu menu = new Menu(shell, SWT.POP_UP);
    tree.setMenu(menu);
    for (int i = 0; i < 12; i++) {
      TreeItem item = new TreeItem(tree, SWT.NONE);
      item.setText("Item " + i);
    }
    menu.addListener(SWT.Show, new Listener() {
      public void handleEvent(Event event) {
        MenuItem[] menuItems = menu.getItems();
        for (int i = 0; i < menuItems.length; i++) {
          menuItems[i].dispose();
        }
        TreeItem[] treeItems = tree.getSelection();
        for (int i = 0; i < treeItems.length; i++) {
          MenuItem menuItem = new MenuItem(menu, SWT.PUSH);
          menuItem.setText(treeItems[i].getText());
        }
      }
    });
    tree.setSize(200, 200);
    shell.setSize(300, 300);
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    display.dispose();
  }
}