code: protected boolean isValidRememberMeCookie(String userKey, String expireDate) {
          final String currentDate = formatForRememberMeExpireDate(timeManager.currentHandyDate());
          if (currentDate.compareTo(expireDate) < 0) { // String v.s. String
              return true; // valid access token within time limit
          }
          // expired here
          logger.debug("The access token for remember-me expired: userKey={} expireDate={}", userKey, expireDate);
          return false;
      }
docs: Are the user ID and expire date extracted from cookie valid?
  @param userKey The key of the login user. (NotNull)
  @param expireDate The string expression for expire date of remember-me access token. (NotNull)
  @return Is a validation for remember-me OK?