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