Christophe Schmaltz created COLLECTIONS-663:
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Summary: 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
{{multimap.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.
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