code: public void replace(int start, int limit, char[] chars,
                          int charsStart, int charsLen) {
          buf.delete(start, limit);
          buf.insert(start, chars, charsStart, charsLen);
      }
docs: Replace a substring of this object with the given text.
  @param start the beginning index, inclusive; <code>0 &lt;= start
  &lt;= limit</code>.
  @param limit the ending index, exclusive; <code>start &lt;= limit
  &lt;= length()</code>.
  @param chars the text to replace characters <code>start</code>
  to <code>limit - 1</code>
  @param charsStart the beginning index into <code>chars</code>,
  inclusive; <code>0 &lt;= start &lt;= limit</code>.
  @param charsLen the number of characters of <code>chars</code>.