On Wed, 8 Jul 2026 21:48:15 GMT, Daisuke Yamazaki <[email protected]> wrote:
>> Ah, yes, good point. So that means that if we check the exact type of `c`
>> then we can trust its `isEmpty()` (need to amend that) and as well not have
>> to check for null elements. So adding a Pq to a PQ should then be as optimal
>> as can be.
>
> Agreed. Thanks for pointing out that.
> I've added a separate fast path for exact `PriorityQueue` sources.
I haven't thought too deeply about this, but I presume you're targeting
something like the following (untested):
@Override
public boolean addAll(Collection<? extends E> c) {
if (getClass() == PriorityQueue.class && size == 0) { // fastpath
if (Objects.requireNonNull(c) == this) // disallow null origins and
self-concatenation
throw new IllegalArgumentException();
Object[] es;
int len;
if (c.isEmpty() || (es = c.toArray()) == null || (len = es.length)
== 0)
return false; // no TOCTOU problem calling c.isEmpty() as it is
an early exit without modification
final Class<?> cType = c.getClass();
if (cType == PriorityQueue.class || cType == ArrayList.class)
; // origin produces a trusted array
else
es = Arrays.copyOf(es, len); // avoid TOCTOU
if (cType == PriorityQueue.class)
; // origin already disallows nulls
else {
for (var e : es)
Objects.requireNonNull(e); // reject any nulls
}
if (cType == PriorityQueue.class &&
((PriorityQueue<?>)c).comparator == comparator)
; // origin already has items in correct order
else
heapify(es, len, comparator); // ensure correct order
++modCount;
queue = ensureNonEmpty(es);
size = len;
return true;
}
else
return super.addAll(c); // fallback to default impl
}
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PR Review Comment: https://git.openjdk.org/jdk/pull/31701#discussion_r3547644624
