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https://issues.apache.org/jira/browse/COLLECTIONS-663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16965277#comment-16965277
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Chen edited comment on COLLECTIONS-663 at 11/2/19 9:08 AM:
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Hi,Gary D.Gregory
Read the code, In the AbstractMultiValuedMap.java,
1、AbstractMultiValuedMap.MapIterator() methos will return private
MultiValuedMapIterator class
2、MultiValuedMapIterator class will call
AbstractMultiValuedMap.entries().iterator()
3、AbstractMultiValuedMap.entries() will return private EntryValues class
4、EntryValues class will return LazyIteratorChain overide nextIterator which
call MultiValuedMapEntry class
5、MultiValuedMapEntry class setValue() method throw
UnsupportedOperationException.
so MapIterator.setValue() is not support!
Ithink it is a proplem, Should we solve this problem by submitting a PR?
was (Author: guoping1):
Hi,Gary D.Gregory
See code, In the AbstractMultiValuedMap.java,
1、AbstractMultiValuedMap.MapIterator() methos will return private
MultiValuedMapIterator class
2、MultiValuedMapIterator class will call
AbstractMultiValuedMap.entries().iterator()
3、AbstractMultiValuedMap.entries() will return private EntryValues class
4、EntryValues class will return LazyIteratorChain overide nextIterator which
call MultiValuedMapEntry class
5、MultiValuedMapEntry class setValue() method throw
UnsupportedOperationException.
so MapIterator.setValue() is not support!
Ithink it is a proplem, Should we solve this problem by submitting a PR?
> 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
> Assignee: Bruno P. Kinoshita
> Priority: Trivial
>
> 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
> }
> // innerCollection.add(6); // adding stuff back should
> also work...
> }
> }{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.
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