On Fri, 24 Mar 2023 22:06:06 GMT, Tagir F. Valeev <tval...@openjdk.org> wrote:
>> Stuart Marks has updated the pull request with a new target base due to a >> merge or a rebase. The pull request now contains 96 commits: >> >> - Merge branch 'master' into JDK-8266571-SequencedCollections >> - Optimizations for ReverseOrderListView; check indexes in reversed domain. >> - Wording tweaks to SequencedMap / NavigableMap. >> - Change "The implementation in this class" to "... interface." >> - Delegate more methods in the views of ReverseOrderSortedMapView. >> - Add missing @throws and @since tags. >> - Convert code samples to snippets. >> - Various editorial changes. >> - Fix up toArray(T[]) on reverse-ordered views. >> - Remove unnecessary 'final' from a couple places. >> - ... and 86 more: https://git.openjdk.org/jdk/compare/2ea62c13...2827aa69 > > src/java.base/share/classes/java/util/ReverseOrderListView.java line 168: > >> 166: boolean modified = false; >> 167: for (E e : c) { >> 168: base.add(0, e); > > This is worrysome from performance point of view for base implementations > like ArrayList where every insertion means shifting the whole array. At > least, we could optimize if `c` is `SequencedCollection`, like `if (c > instanceof SequencedCollection<? extends E> sc) base.addAll(0, > sc.reversed())`. Otherwise, we can use `base.addAll(0, > Arrays.asList(sc.toArray()).reversed())` (with a couple of unchecked casts). Fixed. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/7387#discussion_r1175897522
