code: public static String escapeJSONString(final String unsafeStr) {
          final StringBuilder buf = new StringBuilder(unsafeStr.length() * 2);
          escapeJSONString(unsafeStr, buf);
          return buf.toString();
      }
docs: Escape a string to be surrounded in double quotes in JSON.
  
  @param unsafeStr
  The string to escape.
  @return The escaped string.