code: public void setSeverity(byte severity) throws IllegalArgumentException {
  		if (severity < SyslogMessage.SEVERITY_EMERGENCY
  				|| severity > SyslogMessage.SEVERITY_DEBUG) {
  			throw new IllegalArgumentException("Not a valid severity.");
  		}
  
  		this.severity = severity;
  	}
docs: Get the severity at which the message shall be sent.
  
  @param severity
  the severity to set
  @throws IllegalArgumentException
  if the severity is not a valid severity.