Collectors update

[Kevin Bourrillion]

I'm going to have to frequently apologize for the circular nature of many
of my comments. I wish that I'd always had time to follow the discussions
from the start.


On Thu, Jan 31, 2013 at 2:37 PM, Brian Goetz <brian.goetz at oracle.com> wrote:

> Just throwing this out there: Have we already strongly considered the
>> heretical idea of just naming it reduce()?
>>
>
> Yes.  There are a few reasons we leaned towards a different name here.
>
> 1.  (Pedagogical): The *mutable* reduce-like/fold-like methods have a
> different feel than the more functional analogues.
>

Do they truly, from the consuming perspective? I'm not sure.



> 2.  (Practical): Overloading methods that take the same-shape lambdas
> causes use-site ambiguity problems.  Since there are reduce forms that look
> suspiciously like collect forms, this was an issue.
>
>  It's distinguished from the others by the type it takes (and that's not
>> a lambda-able type so no worries on that front).
>>
>
> No, because there's the multi-arg collect() form.  Which is not only
> useful (collect(ArrayList::new, ArrayList::add, ArrayList::addAll)) but
> also usefully pedagogically (in that the single-arg collect then becomes
> clearly a generalization of the three-arg one.)


I strongly question the idea that that three-arg collect() method is
helping anyone pedagogically. I've come across it many times and even I
don't have the patience to sit down and try to puzzle out what it does and
why I need it. (That's my reaction to probably 50% of the API, btw.)   Why
is it a collect() method instead of just another way to get a Collector?


If we were uncomfortable calling the type accepted Reducer, perhaps
>
>> there's... MutatingReducer.  Bleh.
>>
>
> We had that once!  MutableReduce, it was.  Though mutableReduceUnordered
> is a mouthful.
>

 And again, I'm not sure that the extra word is needed from the consumer's
perspective; more for the implementor (of the thing now called Collector).


-- 
Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com