code: public void setTimestamp(Timestamp timestamp) {
          if (timestamp == null) {
              _properties.remove(AMQP_PROP_TIMESTAMP);
              return;
          }
          
          _properties.put(AMQP_PROP_TIMESTAMP, timestamp);
      }
docs: Sets the value of "timestamp" property. If a null value is passed
  in, it indicates that the property is not set.
  
  @param  timestamp    value of "timestamp" property