On Mon, 19 Oct 2026 16:39:36 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). > > Srikanth Palutla has updated the pull request incrementally with one > additional commit since the last revision: > > Move singleton Comparable check into initElementsFromCollection src/java.base/share/classes/java/util/PriorityQueue.java line 304: > 302: Comparable<? super E> e = (Comparable<? super E>) es[0]; > 303: e.compareTo((E) es[0]); > 304: } Wouldn't it be sufficient to say: if (len == 1 && this.comparator == null && !(es[0] instanceof Comparable)) throw new ClassCastException("class " + es[0].getClass().getName() + " cannot be cast to " + Comparable.getClass().getName()); ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/32966#discussion_r4317186545
