Setting of UNORDERED on concurrent collectors

[Brian Goetz]

That option is always available regardless of what we do with Collectors.

Remember, where Collector really shines is not the simple things like 
this, but composite collections, like

   Map<Buyer, Map<Seller, Transaction>>
     biggestTransactionByBuyerSeller =
       stream.collect(groupingBy(Txn::buyer,
                                 groupingBy(Txn::seller,
                                            maxBy(comparing(Txn::amount))

The groupBy combinator lets you compose complex collections out of 
building blocks.  These would have to be manually inlined with the 
explicit parallel forEach version.


On 4/8/2013 4:57 PM, Doug Lea wrote:
> On 04/08/13 16:41, Joe Bowbeer wrote:
>
>> I'm OK with this, but I wish groupingByConcurrent could go away.
>>
>
> These were the kinds of thoughts that led me last fall to suggest
> that we just tell people to do it themselves as a little idiom:
>    chm = ...
>    c.parallelStream().forEach( chm.merge(x->keyFor(x), x, mergefn); }
>
> The main downside is that this, the most commonly recommended
> way of doing parallel groupBy, would not be in the family of
> collect methods. Still maybe worth reconsidering though.
>
> -Doug
>