Constructing parallel streams

[Remi Forax]

On 12/10/2012 05:01 PM, Joe Bowbeer wrote:
>
> I can easily imagine a pipeline that has alternating 
> sequential/parallel/sequential segments.  Is there any reason to 
> discourage a programmer from using the parallel/sequential methods to 
> express this?
>

You don't need a method sequential() or parallel() for that, you can use 
into.

parallelStream.into(new ArrayList<>()).stream() is now sequential
stream.into(new ArrayList<>()).parallel() is now parallel

and into() offer a better control on the intermediary data structure.


Rémi

> On Dec 10, 2012 7:50 AM, "Brian Goetz" <brian.goetz at oracle.com 
> <mailto:brian.goetz at oracle.com>> wrote:
>
>         I don't like users being able to call parallel in the middle
>         of the
>         stream construction.
>
>
>     I don't love it either.  The semantics are perfectly tractible,
>     and the implementation is perfectly straightforward, but the
>     performance is unlikely to be a win in most cases.  (I mentioned
>     earlier we would doc that this really should only be done at the
>     head of the pipeline.)
>
>         I propose to have an interface ParallelizableStream that allows to
>         choose if the user want the sequential or the parallel stream
>         upfront.
>
>
>     Yeah, we investigated this direction first.  Combinatorial
>     explosion: IntParallelizableStream, etc.
>
>     However, this could trivially become a dynamic property of streams
>     (fits easily into the existing stream flags mechanism).  Then only
>     the head streams would have the property, and if you tried to do
>     parallel() farther down the stream, we could ignore it or even
>     throw ISE.
>