code: @Override
    public <R> StreamBuilderImpl<R,U>
    collect(SupplierSync<R> init,
            BiConsumerSync<R,T> accum,
            BiConsumerSync<R,R> combiner)
    {
      return new CollectSync<>(this, init, accum, combiner);
    }
docs: /*
  @Override
  public <R> StreamBuilderImpl<R,U>
  reduce(R identity,
  BiFunctionAsync<R, ? super T, R> accumulator,
  BinaryOperatorAsync<R> combiner)
  {
  return new ReduceAccumAsync<>(this, identity, accumulator, combiner);
  }