*     sequence.length()}
   * @return the index of the first matching character, guaranteed to be no less than {@code start},
   *     or {@code -1} if no character matches
   * @throws IndexOutOfBoundsException if start is negative or greater than {@code
   *     sequence.length()}
   */
  public int indexIn(CharSequence sequence, int start) {
    int length = sequence.length();
    checkPositionIndex(start, length);