I don't understand why I get a ConcurrentModificationException when I iterate through this `multimap`.
I read the following [entry](http://google-collections.googlecode.com/svn/trunk/javadoc/com/google/common/collect/Multimaps.html#synchronizedMultimap%28com.google.common.collect.Multimap%29), but I am not sure if I understood the whole thing. 
I tried to add a synchronized block. But my doubt is what to synchronize with, and when. 

The `multimap` is a field and created like this : 

```
private Multimap<GenericEvent, Command> eventMultiMap =   
   Multimaps.synchronizedMultimap(HashMultimap.<GenericEvent, Command> create());

```

and used like this : 

```
eventMultiMap.put(event, command);

```

and like this ( I tried to synchronize this part on the map, but without success )

```
for (Entry<GenericEvent, Command> entry : eventMultiMap.entries()) {
    if (entry.getValue().equals(command)) {
        eventMultiMap.remove(entry.getKey(), entry.getValue());
        nbRemoved++;
    }
}

```