RFR: 8266571: Sequenced Collections [v7]

[Stuart Marks]

On Wed, 19 Apr 2023 09:43:44 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> Stuart Marks has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - Remove unnecessary 'final' from a couple places.
>>  - Clarify ordering of Collection.addAll and Map.putAll; add links to
>>    encounter order.
>>  - Make constructors private for several reverse-ordered views.
>
> src/java.base/share/classes/java/util/SequencedCollection.java line 1:
> 
>> 1: /*
> 
> I wonder if there's a point to mention the relation of reversal to the "enhanced for-each" loop. The loop uses the iterator behind the scenes. That means that a reversed collection will iterate backwards in a loop ("enhanced each-for" loop :) ). A backwards iteration can be achieved by
> 
> for (E element : collection.reversed()) {...}
> 
> For collections that support removal, this construct can also be used to remove elements without the concurrent modification problem of removal during iteration which messes up the indices. See, for example, https://stackoverflow.com/questions/10431981/remove-elements-from-collection-while-iterating.

Can't remove using the iterator since it's hidden, and can't remove directly from the collection during iteration without potentially suffering CME. The reverse-iteration trick for removal generally only works for index-based iteration. Not sure what would be useful to add here.

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PR Review Comment: https://git.openjdk.org/jdk/pull/7387#discussion_r1171694499