Method exponent

src/main/java/org/sfj/JSONOne.java:718–728

(StringBuilder ret)

    }

    private void exponent(StringBuilder ret) {
      if (Character.toUpperCase(peek()) == 'E') {
        ret.append(advance());
        if (peek() == '-') {
          ret.append(advance());
        } else if (peek() == '+') {
          ret.append(advance());
        }
        digits(ret);
      }
    }

    private String integer(char first, StringBuilder ret) {
      ret.append(first);