docs: public final String toJsonStringAndClose(
      final Reader source) throws Exception {
      StringBuffer sb = new StringBuffer();
      int chi;
      boolean isStartSpaces = false;
      while ((chi = source.read()) != -1) {
        char ch = (char) chi;
        isStartSpaces = addJsonChar(ch, sb, isStartSpaces);
      }
      source.close();
      return sb.toString();
    }