ConcurrentModificationException

[markini]

Caused by java.util.ConcurrentModificationException
java.util.ArrayList$Itr.next (ArrayList.java:860)
jonathanfinerty.once.Once.beenDone (Once.java:254)
jonathanfinerty.once.Once.beenDone (Once.java:219)
jonathanfinerty.once.Once.beenDone (Once.java:204)
...

"Culprit" is the list inside the map in PersistedMap.java
https://github.com/jonfinerty/Once/blob/master/once/src/main/java/jonathanfinerty/once/PersistedMap.java#L18

Synchronizing access to the list at it is now, could be a little bit of a pain.

Might consider annotating every public static function in Once.java with synchronized. I think this step would at worst cost only a few milliseconds.

[jonfinerty]

More than a year later, I think this is fixed in the 1.3.1 version, if not feel free to reopen