private static String badPositionIndexes(int start, int end, int size) {
    if (start < 0 || start > size) {
      return badPositionIndex(start, size, "start index");
    }
    if (end < 0 || end > size) {
      return badPositionIndex(end, size, "end index");
    }
    // end < start
    return "end index (" + end + ") must not be less than start index (" + start + ")";
  }
private static String badPositionIndexes(int start, int end, int size)