static int compareCharIterators(Iterator<Char> i1, Iterator<Char> i2) {
  while true {
    if (!i1.hasNext())
      ret it2.hasNext() ? -1 : 0;
    if (!it2.hasNext()) ret 1;
    char a = it1.next(), b = it2.next();
    if (a < b) ret -1;
    if (a > b) ret 1;
  }
  ret 0;
}