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https://issues.apache.org/jira/browse/COLLECTIONS-3?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12509351
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Henri Yandell commented on COLLECTIONS-3:
-----------------------------------------
That should be:
synchronized(map) {
Playing with SoakLRUMap, not doing that gives a
ConcurrentModificationException, which hasn't been reported so far.
Mostly I get IllegalStateExceptions when playing with SoakLRUMap and not
synchronizing the Map, however I did get one NPE still:
java.lang.NullPointerException
at org.apache.commons.collections.map.LRUMap.moveToMRU(LRUMap.java:194)
at
org.apache.commons.collections.map.LRUMap.updateEntry(LRUMap.java:217)
Line is:
entry.before.after = entry.after;
Which, looking at the code, implies that entry.before is null. Maybe another
place to put a state check?
Maybe a state check would be worth it there too?
> NPE: map.LRUMap.reuseMapping(LRUMap.java:272)
> ---------------------------------------------
>
> Key: COLLECTIONS-3
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-3
> Project: Commons Collections
> Issue Type: Bug
> Components: Map
> Affects Versions: 3.1
> Environment: Operating System: Linux
> Platform: PC
> Reporter: Otis Gospodnetic
> Attachments: commons-collections-3.2-LRUMap-debug.jar, LRUMap.java,
> SoakLRUMap.java
>
>
> I'm using Collections 3.1 and just found this NPE in my logs:
> java.lang.NullPointerException
> at
> org.apache.commons.collections.map.LRUMap.reuseMapping(LRUMap.java:272)
> at
> org.apache.commons.collections.map.LRUMap.addMapping(LRUMap.java:243)
> at
> org.apache.commons.collections.map.AbstractHashedMap.put(AbstractHashedMap.java:282)
> I instantiated LRUMap like this:
> LRUMap map = new LRUMap(31);
> And from there on, I use it like I'd use any Map, putting things into
> it, and so on. Maybe I'm not using LRUMap correctly? My _guess_ is
> that this occurs when the Map is full, but I am not certain.
> I am wrapping the LRUMap in my own Maps as follows, but I think they're
> not the culprit:
> LRUMap map = new LRUMap(31);
> _userSessions = new ExpiringMap(map,
> new TimerTTLReferenceHolder(1800000), // ttl=30min
> 300000); // purge frequency=5min
> The only similar thing I found is COM-1288, but it looks like that was fixed
> before 3.1 release.
> I understand the value of a self-contained unit test that demonstrates this
> bug,
> but it happens only occassionally on my production system, never during
> development, so I can't really come up with it :(
> My guess is that this is a boundary case, as line 272 is:
> loop = loop.next;
> So 'loop' is most likely null, and it's null because ... not sure, maybe that
> hashIndex is wrong.
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