static int compareCharIterators(Iterator<Char> it1, Iterator<Char> it2) {
  while true {
    if (!it1.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;
  }
}

static int compareCharIterators(CharacterIterator it1, CharacterIterator it2) {
  while true {
    if (!it1.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;
  }
}

static int compareCharIterators(CharacterIterator it1, CharacterIterator it2, CharComparator comparator) {
  if (comparator == null) ret compareCharIterators(it1, it2);
  
  while true {
    if (!it1.hasNext())
      ret it2.hasNext() ? -1 : 0;
    if (!it2.hasNext()) ret 1;
    char a = it1.next(), b = it2.next();
    int cmp = comparator.compare(a, b);
    if (cmp != 0) ret cmp;
  }
}