On Wed, 4 Nov 2020 08:53:23 GMT, Zheka Kozlov <github.com+761899+orio...@openjdk.org> wrote:
>> 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. > > Changes requested by orio...@github.com (no known OpenJDK username). Looking at the linked issue, I see [this comment from Rémi Forax](https://bugs.openjdk.java.net/browse/JDK-8180352?focusedCommentId=14171626&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14171626): > Please talk with Brian about this change because it nulls a property of the > Stream API we (the lambda-util group) have take time to keep. The whole Stream API doesn't depends on the Collection API, [...] so the Stream API can be easily integrated with other collection API if in the future we want by example add a persistent collection API with no link with java.util.List. That's an argument I can understand – as is, the Stream API works just as well with collections from e.g. Scala's or Kotlin's (or Ceylon's) collection libraries instead of the java.util ones, just using different collectors. Adding a method which directly returns a java.util.List somewhat couples it to the Java Collection API. Now this was mentioned two and a half year ago. Did something change which made this consideration irrelevant? I would expect at least some mention of it in the discussion here. ------------- PR: https://git.openjdk.java.net/jdk/pull/1026
