[ https://issues.apache.org/jira/browse/COLLECTIONS-663?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Christophe Schmaltz updated COLLECTIONS-663: -------------------------------------------- Description: Testcase: {code} @Test public void test() { MultiValuedMap<Integer, Integer> multiMap = new HashSetValuedHashMap<>(); multiMap.put(1, 10); multiMap.put(2, 20); for (Collection<Integer> innerCollection : multiMap.asMap().values()) { for (Iterator<Integer> iterator = innerCollection.iterator(); iterator.hasNext();) { Integer i = iterator.next(); iterator.remove(); // only the innerCollection is altered } } }{code} This test unexpectedly throws a ConcurrentModificationException. The issue is that when calling {{iterator.remove()}} the {{AbstractMultiValuedMap.ValuesIterator}} detects that the Collection is empty and calls {{AbstractMultiValuedMap.this.remove(key);}}. It may be better if the iterator of the inner collection had a reference on the iterator if the outer map and called {{containerIterator.remove()}} instead. *Note:* this solution would again present issues if the user tries to add new elements in this now empty collection (which was removed from the parent). In the current state, it is quite unclear why an exception is thrown, without debugging the code. was: Testcase: {code} @Test public void test() { MultiValuedMap<Integer, Integer> multiMap = new HashSetValuedHashMap<>(); multiMap.put(1, 10); multiMap.put(2, 20); for (Collection<Integer> innerCollection : multiMap.asMap().values()) { for (Iterator<Integer> iterator = innerCollection.iterator(); iterator.hasNext();) { Integer i = iterator.next(); iterator.remove(); // only the innerCollection is altered } } }{code} This test unexpectedly throws a ConcurrentModificationException. The issue is that when calling {{iterator.remove()}} the {{AbstractMultiValuedMap.ValuesIterator}} detects that the Collection is empty and calls {{AbstractMultiValuedMap.this.remove(key);}}. It would be better if the iterator of the inner collection had a reference on the iterator if the outer map and called {{containerIterator.remove()}} instead. In the current state, it is quite unclear why an exception is thrown, without debugging the code. > Unexpected ConcurrentModificationException when altering Collection of a > MultiValuedMap > --------------------------------------------------------------------------------------- > > Key: COLLECTIONS-663 > URL: https://issues.apache.org/jira/browse/COLLECTIONS-663 > Project: Commons Collections > Issue Type: Bug > Reporter: Christophe Schmaltz > > Testcase: > {code} @Test > public void test() { > MultiValuedMap<Integer, Integer> multiMap = new > HashSetValuedHashMap<>(); > multiMap.put(1, 10); > multiMap.put(2, 20); > for (Collection<Integer> innerCollection : > multiMap.asMap().values()) { > for (Iterator<Integer> iterator = > innerCollection.iterator(); iterator.hasNext();) { > Integer i = iterator.next(); > iterator.remove(); // only the innerCollection > is altered > } > } > }{code} > This test unexpectedly throws a ConcurrentModificationException. > The issue is that when calling {{iterator.remove()}} the > {{AbstractMultiValuedMap.ValuesIterator}} detects that the Collection is > empty and calls {{AbstractMultiValuedMap.this.remove(key);}}. > It may be better if the iterator of the inner collection had a reference on > the iterator if the outer map and called {{containerIterator.remove()}} > instead. > *Note:* this solution would again present issues if the user tries to add new > elements in this now empty collection (which was removed from the parent). > In the current state, it is quite unclear why an exception is thrown, without > debugging the code. -- This message was sent by Atlassian JIRA (v6.4.14#64029)