*/
    @SuppressWarnings("unchecked")
    ImmutableList<E> buildSorted(Comparator<? super E> comparator) {
      // Currently only used by ImmutableListMultimap.Builder.orderValuesBy.
      // In particular, this implies that the comparator can never get "removed," so this can't
      // invalidate future builds.

      copyOnWrite = true;
      Arrays.sort((E[]) contents, 0, size, comparator);