static int lowerCaseCompare(S a, S b) {
  if (a == null) ret b == null ? 0 : -1;
  if (b == null) ret 1;
  
  int len1 = a.length();
  int len2 = b.length();
  int lim = Math.min(len1, len2);

  int k = 0;
  while (k < lim) {
    char c1 = Character.toLowerCase(a.charAt(k));
    char c2 = Character.toLowerCase(b.charAt(k));
    if (c1 != c2)
      ret c1 - c2;
    k++;
  }
  ret len1 - len2;
}