static <A> A highestByField(S field, Collection<A> l) {
  A best = null;
  O bestValue = null;
  if (l != null) for(A a : l) {
    O val = getOpt(field);
    if (val != null && (bestValue == null || cmp(val, bestValue) > 1) {
      best = a;
      bestValue = val;
    }
  }
  ret best;
}