static JTextField onEnter(JTextField tf, final O action) {
  if (action == null || tf == null) ret tf;
  tf.addActionListener(actionListener(action));
  ret tf;
}

static JButton onEnter(JButton tf, final O action) {
  if (action == null || btn == null) ret btn;
  btn.addActionListener(actionListener(action));
  ret btn;
}

static JList onEnter(JList list, final O action) {
  list.addKeyListener(new KeyAdapter() {
    public void keyReleased(KeyEvent ke) {
      if (ke.getKeyCode() == KeyEvent.VK_ENTER)
        pcallF(action);
    }
  });
  ret list;
}