Shortcuts on Collections to create Streams
brian.goetz at oracle.com
Thu Mar 4 18:54:10 UTC 2021
We are extremely conservative about adding "convenience" methods; in
general, they don't carry their weight. There are exceptions, but these
have to be justified carefully.
Your original mail illustrates one of the many problems with convenience
methods: every one we add leads to a call for more:
> As Collection already has a default implementation for 'forEach', I'm
> wondering why there is no similar shortcuts for a couple of repeating
> patterns around the Collection <--> Stream transitions?
But a world with the union of all possible convenience methods that
someone could imagine being useful, is not the world we want to live in;
both library implementors and users would be overwhelmed with trivial
differences, and this crowds out higher-value activities. In general, we
prefer to expose the primitives, and let users combine them, though
different JDK libraries follow this to different degrees. But, in
general, a "trivial" method requires a nontrivial amount of justification.
On 3/4/2021 1:56 AM, Zs. wrote:
> Thanks, so I'm late by about 4 months for that method.
> I've found the tickets about this for future reference:
> and the pull request - https://github.com/openjdk/jdk/pull/1026
> Now, I only miss the 3 other what I've mentioned :)
> Best regards,
> On Wed, Mar 3, 2021 at 10:53 PM Thiago Henrique Hupner <thihup at gmail.com>
>> They have added the Stream#toList in JDK 16:
>> Em qua., 3 de mar. de 2021 às 18:45, Zs. <gzsombor at gmail.com> escreveu:
>>> As Collection already has a default implementation for 'forEach', I'm
>>> wondering why there is no similar shortcuts for a couple of repeating
>>> patterns around the Collection <--> Stream transitions?
>>> For example, if you could write:
>>> collection.map(...) instead of collection.stream().map(...);
>>> collection.filter(...) instead of collection.stream().filter(...);
>>> Or for the other direction:
>>> stream.toList() instead of stream.collect(Collectors.toList())
>>> stream.toSet() instead of stream.collect(Collectors.toSet())
>>> They are heavily used even in OpenJDK's source code:
>>> - 380 results, unfortunately with false matches from javax.xml.stream.
>>> - 559 results, unfortunately with false matches from comments or
>>> streams().mapToInt or not related code
>>> - 367 results
>>> - 117 results
>>> Any particular reason, why adding these - 4 or more - default method to a
>>> collection deemed unnecessary or harmful? Unfortunately I haven't been
>>> to find the answers for this question using internet searches.
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