static <A extends Container> A addComponents(A c, Cl<? extends Component> components) {
  if (nempty(components)) swing {
    for (Component comp : components)
      if (comp != null)
        c.add(comp);
    revalidate(c);
  }
  ret c;
}

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