*
   * @since 11.0
   */
  public static String commonSuffix(CharSequence a, CharSequence b) {
    checkNotNull(a);
    checkNotNull(b);

    int maxSuffixLength = min(a.length(), b.length());
    int s = 0;
    while (s < maxSuffixLength && a.charAt(a.length() - s - 1) == b.charAt(b.length() - s - 1)) {
      s++;
    }
    if (validSurrogatePairAt(a, a.length() - s - 1)