* @param replacement the character to append to the result string in place of each matching
   *     character in {@code sequence}
   * @return the new string
   */
  public String replaceFrom(CharSequence sequence, char replacement) {
    String string = sequence.toString();
    int pos = indexIn(string);
    if (pos == -1) {
      return string;
    }
    char[] chars = string.toCharArray();
    chars[pos] = replacement;

   * @param replacement the character to append to the result string in place of each matching
   *     character in {@code sequence}
   * @return the new string
   */
  public String replaceFrom(CharSequence sequence, char replacement) {
    String string = sequence.toString();
    int pos = indexIn(string);
    if (pos == -1) {
      return string;
    }
    char[] chars = string.toCharArray();
    chars[pos] = replacement;