static <A extends Component> A internalFrameTitle(A c, S title) {
  JInternalFrame f = getInternalFrame(c);
  if (f != null) swing { f.setTitle(unnull(title)); }
}

static <A extends Component> A internalFrameTitle(S title, A c) {
  ret internalFrameTitle(c, title);
}

static S internalFrameTitle(Component c) {
  final JInternalFrame f = getInternalFrame(c);
  ret f == null ? null : swing(func -> S { f.getTitle() });
}