Solved Concurrent modification

I am working on making cooldowns. However, I keep getting throw a concurrent modification error. This error is due to the for loop I'm using then I modify it. However, I'm not sure of any other way to do it. Here is the code:

Code:java

BukkitScheduler scheduler = Bukkit.getServer().getScheduler();
            scheduler.scheduleSyncRepeatingTask(this, new Runnable() {
                @Override
                public void run() {
                for (UUID u : playerz.keySet()){  //playerz is a hashmap
                    for (String s : playerz.get(u).keySet()){//players.get(u) returns a hashmap and line that is causing the error
                        int i = playerz.get(u).get(s);
                        i--;
                        if (i <= 0){
                            playerz.get(u).remove(s);
                            if (playerz.get(u).isEmpty()){
                                playerz.remove(u);
                            }
 
                        }else{
                            playerz.get(u).put(s, i);
                        }
                    }
                }
                }
            }, 0L, 20L);

Error:

Code:

12.10 21:13:59 [Server] INFO at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [cbukkit.jar:git-Bukkit-1.7.9-R0.2-20-g0b2ed13-b3108jnks][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:469) [cbukkit.jar:git-Bukkit-1.7.9-R0.2-20-g0b2ed13-b3108jnks][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:558) [cbukkit.jar:git-Bukkit-1.7.9-R0.2-20-g0b2ed13-b3108jnks][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:258) [cbukkit.jar:git-Bukkit-1.7.9-R0.2-20-g0b2ed13-b3108jnks][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:600) [cbukkit.jar:git-Bukkit-1.7.9-R0.2-20-g0b2ed13-b3108jnks][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:349) [cbukkit.jar:git-Bukkit-1.7.9-R0.2-20-g0b2ed13-b3108jnks][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftTask.run(CraftTask.java:53) ~[cbukkit.jar:git-Bukkit-1.7.9-R0.2-20-g0b2ed13-b3108jnks][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at tfw.CC.Main$1.run(Main.java:33) ~[?:?][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at java.util.HashMap$KeyIterator.next(Unknown Source) ~[?:1.8.0_05][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO at java.util.HashMap$HashIterator.nextNode(Unknown Source) ~[?:1.8.0_05][/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO java.util.ConcurrentModificationException[/COLOR]
[COLOR=#2c2c2c]12.10 21:13:59 [Server] INFO [21:13:59 WARN]: [CommandCooldown] Task #21023 for CommandCooldown v1.0 generated an exception

Thanks![/CODE][/COLOR]

 

http://docs.oracle.com/javase/7/docs/api/java/util/ConcurrentModificationException.html

You are removing the UUID while iterating over it.

 

I know why the issue is occurring, I am wondering how to have the code do that same thing, while not throwing an exception.

 

ConcurrentModificationExceptions happen when you add or remove elements from a collection (HashMap in this case) while iterating over it. Example:

Code:java

HashMap<String, String> map = new HashMap<String, String>();
//...
for(String key : map.keySet()) {
    map.remove(key); //ConcurrentModificationException!
}

There are a few ways around this but my preferred way is to clone the map, iterate over the clone, and modify the original.

Code:java

HashMap<String, String> map = new HashMap<String, String>();
//...
HashMap<String, String> clonedMap = new HashMap<String, String>(map); //I think this works?
for(String key : clonedMap.keySet()) {
    map.remove(key);
}

 

Sorry i misunderstood.

 

rbrick adam753 Fixed with a list iterator. Works like a charm! Thanks for the help!

 

The Fancy Whale was just about to post that