code: public static boolean allSameSize(List<Collection<?>> collections) {
      if (collections.isEmpty()) {
        return true;
      }
      final int referenceSize = collections.get(0).size();
      for (final Collection<?> col : collections) {
        if (col.size() != referenceSize) {
          return false;
        }
      }
      return true;
    }
docs: Returns true if and only if all the collections in the provided list have the same size.
  Returns true if the provided list is empty.