class Jwt {

  public String getAlgorithm() throws JwtExpiredException, JwtNotBeforeException {
    validateTimestampClaims();

    try {
      return header.getString(JwtNames.HEADER_ALGORITHM);
    } catch (JSONException ex) {
      throw new IllegalStateException("an alg header is required, but not found", ex);
    }
  }

    Jwt(JSONObject header, JSONObject payload, Clock clock, Duration clockSkew);

}