public static void registerUpDownHint(JComponent component, final GrTypeComboBox combo) {
    final AnAction arrow = new AnAction() {
      @Override
      public void actionPerformed(@NotNull AnActionEvent e) {
        if (e.getInputEvent() instanceof KeyEvent) {
          final int code = ((KeyEvent)e.getInputEvent()).getKeyCode();
          scrollBy(code == KeyEvent.VK_DOWN ? 1 : code == KeyEvent.VK_UP ? -1 : 0, combo);
        }
      }
    };
    final KeyboardShortcut up = new KeyboardShortcut(KeyStroke.getKeyStroke(KeyEvent.VK_UP, InputEvent.ALT_DOWN_MASK), null);
    final KeyboardShortcut down = new KeyboardShortcut(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, InputEvent.ALT_DOWN_MASK), null);
    arrow.registerCustomShortcutSet(new CustomShortcutSet(up, down), component);
  }
public static void registerUpDownHint(JComponent component, final GrTypeComboBox combo)