static <A> L<A> sortedByFieldAlphaNumDesc(Collection<A> c, final S field) {
  L<A> l = new ArrayList(c);
  sort(l, new Comparator<A>() {
    public int compare(A a, A b) {
      ret alphaNumComparator().compare((S) getOpt(b, field), (S) getOpt(a, field));
    }
  });
  ret l;
}

static <A> L<A> sortedByFieldAlphaNumDesc(S field, Collection<A> c) {
  ret sortedByFieldAlphaNumDesc(c, field);
}