Christophe Schmaltz created COLLECTIONS-663: -----------------------------------------------
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. -- This message was sent by Atlassian JIRA (v6.4.14#64029)