On Sun, 20 Sep 2026 00:54:10 GMT, Srikanth Palutla <[email protected]> wrote:
> Problem > new PriorityQueue<>(List.of(new Object())) succeeds today when it should > throw ClassCastException. initFromCollection relies on heapify() to surface > incomparable elements, but heapify performs no comparisons on a singleton, so > the lone element is never validated. Collections with two or more > non-Comparable elements already throw. > > Fix > In initFromCollection, when the collection holds exactly one element and no > comparator is in play, self-compare the element before heapifying. This > mirrors what TreeMap does for its first key (see JDK-5045147). Behavior with > an explicit comparator is unchanged: non-Comparable elements are still > accepted when a comparator is provided. > > Testing > Added a copyConstructorSingleton regression test to AddNonComparable covering > PriorityQueue(Collection) and PriorityQueue(Collection, Comparator) with a > null comparator, plus the positive cases (Comparable singleton, explicit > comparator). Verified the new test passes against the patched class and the > existing queues() test still passes. > > > Please let me know for further questions > > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai). src/java.base/share/classes/java/util/PriorityQueue.java line 316: > 314: e.compareTo((E) queue[0]); > 315: } > 316: heapify(); Is this the optimal place for this check? Would it not be possible to put this check inside of `initElementsFromCollection`, it would cover more ground than initFromCollection? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/32966#discussion_r4312373448
