brian.goetz at oracle.com
Thu Jun 13 11:21:57 PDT 2013
> - String-specific reductions
> - concatenating()
> - joining x2: delimiter [, prefix, suffix ]
Should we find a name other than joining? "join" has a very database-y
feel to it, and in fact we might want to support some sort of joining in
They could all be called concatenating.
> - Reductions:
> - reducing x3: reducer [, identity [, mapper ] ]
> - minBy(comparator)
> - maxBy(comparator)
Also to discuss: the no-identity version of reducing, as well as
min/max, could now return Optional (they couldn't before.) While the
likelihood of them actually being applied to an empty stream is
considerably lower than for the corresponding methods on Stream (because
these methods are mostly for use as downstream reducers for things like
groupingBy), it is possible that a user will use them directly.
Currently they return null for empty streams.
It seems "obvious" that we should make these bear Optional, but it also
seems a shame, as this will impose a dramatic performance cost on any
groupBy operation that uses them, because it means that every groupBy
using them will be followed by a (sequential) Map.replaceAll. So the
combination of "higher cost" and "wouldn't ever happen in that case
anyway" gives me some pause.
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