code: @Override
    public QueueDeliver<M> build(Deliver<M> deliver)
    {
      validateBuilder();
      
      if (deliver == null) {
        throw new IllegalArgumentException(L.l("'processors' is required"));
      }
      
      QueueRing<M> queue = buildQueue();
      
      Executor executor = createExecutor();
      ClassLoader loader = getClassLoader();
      
      // OutboxDeliver<M> outbox = _outboxFactory.createOutbox(deliver);
      
      WorkerDeliverSingleThread<M> worker
        = new WorkerDeliverSingleThread<M>(deliver,
                                          _outboxContext,
                                          executor,
                                          loader,
                                          queue);
      
      return new QueueDeliverImpl<M>(queue, worker);
    }
docs: /*
  @Override
  public OutboxDeliver<M> createOutbox(Deliver<M> deliver)
  {
  return _outboxFactory.createOutbox(deliver);
  }