JInternalFrameにJPopupMenuを設定してタイトルを変更する

private static JInternalFrame createFrame(String t, int i) {
  JInternalFrame f = new JInternalFrame(t + i, true, true, true, true);
  f.setSize(200, 100);
  f.setLocation(5 + 40 * i, 5 + 50 * i);
  JPopupMenu popup = new InternalFramePopupMenu();
  f.setComponentPopupMenu(popup);
  // ((BasicInternalFrameUI) f.getUI()).getNorthPane().setComponentPopupMenu(popup);
  ((BasicInternalFrameUI) f.getUI()).getNorthPane().setInheritsPopupMenu(true);
  f.getDesktopIcon().setComponentPopupMenu(popup);
  EventQueue.invokeLater(() -> f.setVisible(true));
  return f;
}

class InternalFramePopupMenu extends JPopupMenu {
  protected InternalFramePopupMenu() {
    super();
    JTextField field = new JTextField(24); // { ... };
    String cmd = "Edit Title";
    add(cmd).addActionListener(e -> {
      Component c = getInternalFrame(getInvoker());
      if (c instanceof JInternalFrame) {
        JInternalFrame frame = (JInternalFrame) c;
        field.setText(frame.getTitle());
        Container p = frame.getDesktopPane();
        int ret = JOptionPane.showConfirmDialog(
            p, field, cmd, JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
        if (ret == JOptionPane.OK_OPTION) {
          renameInternalFrameTitle(frame, field.getText().trim());
        }
      }
    });
  }
  // ...
}

private static Component getInternalFrame(Component c) {
  Component f;
  if (c instanceof JInternalFrame.JDesktopIcon) {
    f = ((JInternalFrame.JDesktopIcon) c).getInternalFrame();
  } else if (c instanceof JInternalFrame) {
    f = c;
  } else { // if (c instanceof BasicInternalFrameTitlePane) {
    f = SwingUtilities.getAncestorOfClass(JInternalFrame.class, c);
  }
  return f;
}