code: private void setSerialNumber(Object val) throws CertificateException {
          if (!(val instanceof CertificateSerialNumber)) {
              throw new CertificateException("SerialNumber class type invalid.");
          }
          serialNum = (CertificateSerialNumber)val;
      }
docs: Set the serial number of the certificate.
  
  @params val the Object class value for the CertificateSerialNumber
  @exception CertificateException on invalid data.