Encounter order

[Andrey Breslav]

People don't expect ordering of the *keys*, and that's fine.  What I
>>> was talking about was ordering of the values, since the Map returned
>>> is a Map<K, Collection<V>>.
>> Your reduceBy() looked like this:
>>
>> <U, W> Map<U, W> reduceBy(...)
>>
>> no collections anywhere. Was that a mistake?
>
> groupBy returns a Map<K,Collection<T>>.
>
> reduceBy returns a Map<K,W>, because instead of accumulating elements 
> in a K bucket and sticking them in a collection, we reduce all the 
> elements in the K bucket.
>
> For example:
>
>   Map<Author, Document> longestDocByAuthor
>     = docs.reduceBy(Document::getAuthor,
>                     (d1, d2) -> (d1.length() > d2.length() ? d1 : d2));
>
Yes. And my point was that thus no ordering considerations are 
applicable to the result of reduceBy. Or am I missing something?