Question

Java Programming

Issues With Iterating My Map

Iterator<Player> iterator = plugin.inreview.keySet().iterator();
while (iterator.hasNext()) {
    Player key = (Player) iterator.next();
    chat.getRecipients().remove(key);
}

This throws:

java.util.NoSuchElementException 
    at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
    at java.util.HashMap$EntryIterator.next(Unknown Source)
    at java.util.HashMap$EntryIterator.next(Unknown Source)

Any ideas as to why this is happening? When this occurs, there is one key (with one value) in the map.

Also, it used to work until recently and I have done so much work on my Java file that I have no way to find out what made this occur. I can’t do any while loop when iterating this map which complicates things a ton!

Notes:

• Chat.getRecipients() is not the same as plugin.inreview
• Used to work just fine
• It is a HashBiMap

Please, give me any hints and ideas that you may have.

Extra Details:

java.util.NoSuchElementException
    at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
    at java.util.HashMap$EntryIterator.next(Unknown Source)
    at java.util.HashMap$EntryIterator.next(Unknown Source)
    at com.google.common.collect.AbstractBiMap$EntrySet$1.next(AbstractBiMap.java:314)
    at com.google.common.collect.AbstractBiMap$EntrySet$1.next(AbstractBiMap.java:306)
    at me.geekplaya.Judge.JudgeQuit.onPlayerQuit(JudgeQuit.java:25)
    at org.bukkit.plugin.java.JavaPluginLoader$2.execute(JavaPluginLoader.java:251)
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:58)
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:339)
    at net.minecraft.server.ServerConfigurationManager.disconnect(ServerConfigurationManager.java:159)
    at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:650)
    at net.minecraft.server.NetworkManager.b(NetworkManager.java:231)
    at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:92)
    at net.minecraft.server.NetworkListenThread.a(SourceFile:108)
    at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:471)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)

Answer 1

If the remove call is, as you say, not operating on the iterated sequence then there must be another thread updating plugin.inreview.

Check all write accessors of plugin.review and make sure no concurrent update is possible while a thread is reading using this code.

Note that such a bug could fail to manifest for a long time and then suddenly become a serious issue due to changes elsewhere that affect thread timings.