RFR: 8184166: SortedList does not free up memory

[John Hendrikx]

On Sun, 7 Dec 2025 01:36:02 GMT, Cormac Redmond <duke at openjdk.org> wrote:

> Fix SortedList memory leak by clearing unused entries in the internal array when the source list shrinks. Also nullify tempElement.e after use,
> 
> Adding "--add-opens=javafx.base/javafx.collections.transformation=ALL-UNNAMED" to allow reflection access from tests.

This looks pretty good, I left a remark about how you clear the unused part of the list.

modules/javafx.base/src/main/java/javafx/collections/transformation/SortedList.java line 284:

> 282:                 // Already null, stop checking further
> 283:                 break;
> 284:             }

I think this is unsafe, depending on where the `null`s are sorted in the list (especially with a `nullsFirst` comparator). It may be better to get the `size` at the start of this method, and then clear anything from `size` to `oldSize` unconditionally.

modules/javafx.base/src/test/java/test/javafx/collections/SortedListTest.java line 622:

> 620:         SortedList<String> unsortedSortedList = new SortedList<>(list);
> 621:         assertEquals(0, sortedList.size());
> 622:         assertEquals(0, unsortedSortedList.size());

You could consider making the test parameterized.

modules/javafx.base/src/test/java/test/javafx/collections/SortedListTest.java line 677:

> 675:         checkElementsBeyondSizeAreNull(1, ReflectionUtils.getFieldValue(sortedList, "sorted"));
> 676:         checkElementsBeyondSizeAreNull(1, ReflectionUtils.getFieldValue(unsortedSortedList,
> 677:                 "sorted"));

So I guess that `null`s are sorted towards the end?  I think this will fail when they are sorted near the beginning (won't clear element `z` and `y`).

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PR Review: https://git.openjdk.org/jfx/pull/2000#pullrequestreview-3550364865
PR Review Comment: https://git.openjdk.org/jfx/pull/2000#discussion_r2597245820
PR Review Comment: https://git.openjdk.org/jfx/pull/2000#discussion_r2597241565
PR Review Comment: https://git.openjdk.org/jfx/pull/2000#discussion_r2597240243