static <A extends Container> A addAllComponents(A c, L<? extends Component> components) {
  if (nempty(components)) swing {
    for (Component x : components)
      c.add(x);
    revalidate(c);
  }
  ret c;
}

static <A extends Container> A addAllComponents(A c, Component... components) {
  ret addAllComponents(c, asList(components));
}