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https://issues.apache.org/jira/browse/COLLECTIONS-802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17526562#comment-17526562
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Ben Manes commented on COLLECTIONS-802:
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Caffeine's
[implementation|https://github.com/ben-manes/caffeine/blob/f52062955adb749e7828d1f1cff12a9eea26bee4/caffeine/src/main/java/com/github/benmanes/caffeine/cache/BoundedLocalCache.java#L3452-L3455]
also modified state during the hasNext(), but it caches the next entry and
uses that as a guard condition to only search when null.
> ReferenceMap iterator remove violates contract
> ----------------------------------------------
>
> Key: COLLECTIONS-802
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-802
> Project: Commons Collections
> Issue Type: Bug
> Components: Map
> Affects Versions: 4.4
> Reporter: Ben Manes
> Priority: Minor
> Attachments: ApacheMapTest.java
>
>
> Out of curiosity I ran Guava's testlib Map tests against the Apache types.
> This uncovered a contract bug where {{Iterator.remove()}} is invalidated by
> {{{}hasNext(){}}}, causing its call to no-op due to {{currentKey}} becoming
> {{{}null{}}}. The isolates case is,
> {code:java}
> @Test
> public void iterator_remove() {
> var map = new ReferenceMap<>();
> map.put(1, 2);
> var iter = map.entrySet().iterator();
> assertTrue(iter.hasNext());
> assertTrue(iter.hasNext());
> assertEquals(iter.next(), 1);
> assertFalse(iter.hasNext());
> iter.remove();
> assertEquals(map, Map.of());
> }{code}
> Guava's [testlib|https://github.com/google/guava/tree/master/guava-testlib]
> has good coverage for the Collections Framework and might be worth
> integrating. The simple test case that I wrote is attached.
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