RFR: 8180352: Add Stream.toList() method [v4]

[Remi Forax]

----- Mail original -----
> De: "Stuart Marks" <smarks at openjdk.java.net>
> À: "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Mardi 24 Novembre 2020 08:10:14
> Objet: Re: RFR: 8180352: Add Stream.toList() method [v4]

>> This change introduces a new terminal operation on Stream. This looks like a
>> convenience method for Stream.collect(Collectors.toList()) or
>> Stream.collect(Collectors.toUnmodifiableList()), but it's not. Having this
>> method directly on Stream enables it to do what can't easily by done by a
>> Collector. In particular, it allows the stream to deposit results directly into
>> a destination array (even in parallel) and have this array be wrapped in an
>> unmodifiable List without copying.
>> 
>> In the past we've kept most things from the Collections Framework as
>> implementations of Collector, not directly on Stream, whereas only fundamental
>> things (like toArray) appear directly on Stream. This is true of most
>> Collections, but it does seem that List is special. It can be a thin wrapper
>> around an array; it can handle generics better than arrays; and unlike an
>> array, it can be made unmodifiable (shallowly immutable); and it can be
>> value-based. See John Rose's comments in the bug report:
>> 
>> https://bugs.openjdk.java.net/browse/JDK-8180352?focusedCommentId=14133065&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14133065
>> 
>> This operation is null-tolerant, which matches the rest of Streams. This isn't
>> specified, though; a general statement about null handling in Streams is
>> probably warranted at some point.
>> 
>> Finally, this method is indeed quite convenient (if the caller can deal with
>> what this operation returns), as collecting into a List is the most common
>> stream terminal operation.
> 
> Stuart Marks has updated the pull request incrementally with one additional
> commit since the last revision:
> 
>  Add comment and assert regarding array class; use switch expression.
> 
> -------------

Hi Stuart,
This version is Ok for me.

I still think that using a null friendly List is a mistake, but you, Brian and John all think it's not an issue, so let's go with it.

> 
> Changes:
>  - all: https://git.openjdk.java.net/jdk/pull/1026/files
>  - new: https://git.openjdk.java.net/jdk/pull/1026/files/15beacd2..bd890ae5
> 
> Webrevs:
> - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1026&range=03
> - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1026&range=02-03
> 
>  Stats: 20 lines in 1 file changed: 4 ins; 4 del; 12 mod
>  Patch: https://git.openjdk.java.net/jdk/pull/1026.diff
>  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1026/head:pull/1026
> 
> PR: https://git.openjdk.java.net/jdk/pull/1026