sbool comboBoxItemsAre(JComboBox cb, L l) {
  ret cb != null && swing(func -> bool {
    ComboBoxModel model = cb.getModel();
    if (model.getSize() != l(l)) false;
    for i over l:
      if (neq(model.getElementAt(i), l.get(i))) false;
    true;
  });
}