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). Friendly ping — this has been awaiting review since September. Quick recap: PriorityQueue.initFromCollection never validates a single-element collection (heapify performs no comparisons on a singleton), so new PriorityQueue<>(List.of(new Object())) succeeds where it should throw ClassCastException. The fix self-compares the lone element when no comparator is set, mirroring TreeMap's first-key check (JDK-5045147). All automated checks are green; it just needs a Reviewer. @viktorklang-ora @liach — you both reviewed the recent PriorityQueue constructor work in #31452; if either of you has a few minutes, a review here would be much appreciated. ------------- PR Comment: https://git.openjdk.org/jdk/pull/32966#issuecomment-6246096732
