What the heck is this?

[ttk2]

2013-01-02 13:49:15 [WARNING] [PrisonPearl] Task #23 for PrisonPearl v1.5.1 generated an exception
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:894)
at java.util.HashMap$EntryIterator.next(HashMap.java:934)
at java.util.HashMap$EntryIterator.next(HashMap.java:932)
at com.untamedears.PrisonPearl.SummonManager.inflictSummonDamage(SummonManager.java:94)
at com.untamedears.PrisonPearl.SummonManager.access$0(SummonManager.java:91)
at com.untamedears.PrisonPearl.SummonManager$1.run(SummonManager.java:40)
at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:53)
at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345)
at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:514)
at net.minecraft.server.DedicatedServer.r(DedicatedServer.java:222)
at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:478)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:413)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:856)

[WildWeazel]

Shouldn't that map (SummonManager.summons) be a ConcurrentHashMap? It's being accessed, in inflictSummonDamage from a task scheduler outside of the main thread. Not sure if that will completely resolve the problem (multithreading, yay!), but it's what sticks out to me.

http://docs.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/ConcurrentHashMap.html