Solved Iterating through a Hashmap doesn't work

Hello guys,

I've been trying to iterate through a hashmap and remove the entry, but it prints me an error.
ResetListener Class:

ResetListener Class (open) ResetListener Class (close)

Code:

package de.smoothie2.prison.scheduler;

import java.util.Iterator;
import java.util.Map.Entry;

import org.bukkit.Bukkit;
import org.bukkit.Location;
import org.bukkit.Material;

import de.smoothie2.prison.events.BlockListener;
import de.smoothie2.prison.main.Main;

public class ResetScheduler {
    private static int scheduler;
    private static int i;
    private static boolean isresetting = false;
    public static void start() {
        scheduler = Bukkit.getScheduler().scheduleSyncRepeatingTask(Main.getInstance(), new Runnable() {
            public void run() {
                Bukkit.broadcastMessage("\u00a7bEs werden nun alle \u00a73Minen \u00a7bzurückgesetzt.");
                i = Bukkit.getScheduler().scheduleSyncRepeatingTask(Main.getInstance(), new Runnable() {
                    public void run() {
                        isresetting = true;
                        int c = 0;
                        Iterator<Entry<Location, Material>> it = BlockListener.getBrokenBlocks().entrySet().iterator();
                        while(it.hasNext() && c < 10000) {
                            Entry<Location, Material> map = it.next();
                            map.getKey().getWorld().getBlockAt(map.getKey()).setType(map.getValue());
                            BlockListener.getBrokenBlocks().remove(map.getKey());
                            c++;
                        }
                    }
                }, 0, 20);
                Bukkit.getScheduler().scheduleSyncDelayedTask(Main.getInstance(), new Runnable() {
                    public void run() {
                        Bukkit.getScheduler().cancelTask(i);
                        i = 0;
                        isresetting = false;
                        Bukkit.broadcastMessage("\u00a7bEs wurden erfolgreich alle \u00a73Minen \u00a7bzurückgesetzt.");
                    }
                }, (Math.round(BlockListener.getBrokenBlocks().size()/10000)+1)*20);
            }
        }, 6000, 6000);
    }
    public static void stop() {
        if(scheduler != 0) Bukkit.getScheduler().cancelTask(scheduler);
        scheduler = 0;
    }
    public static boolean isResetting() {
        return isresetting;
    }
}

And the error:

Error (open) Error (close)

Code:

[17:30:52 WARN]: [Prison] Task #12 for Prison v0.1_SNAPSHOT generated an excepti
on
java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextNode(Unknown Source) ~[?:1.8.0_25]

        at java.util.HashMap$EntryIterator.next(Unknown Source) ~[?:1.8.0_25]
        at java.util.HashMap$EntryIterator.next(Unknown Source) ~[?:1.8.0_25]
        at de.smoothie2.prison.scheduler.ResetScheduler$1$1.run(ResetScheduler.j
ava:27) ~[?:?]
        at org.bukkit.craftbukkit.v1_8_R1.scheduler.CraftTask.run(CraftTask.java
:71) ~[spigot.jar:git-Spigot-ed3e3af-ee6d0fa]
        at org.bukkit.craftbukkit.v1_8_R1.scheduler.CraftScheduler.mainThreadHea
rtbeat(CraftScheduler.java:350) [spigot.jar:git-Spigot-ed3e3af-ee6d0fa]
        at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:7
09) [spigot.jar:git-Spigot-ed3e3af-ee6d0fa]
        at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:3
16) [spigot.jar:git-Spigot-ed3e3af-ee6d0fa]
        at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:6
34) [spigot.jar:git-Spigot-ed3e3af-ee6d0fa]
        at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java
:537) [spigot.jar:git-Spigot-ed3e3af-ee6d0fa]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_25]

Thanks for your help,
Smootey ~

 

Moved to Bukkit Alternates.

 

@Smootey Why use a while loop? You can use a for loop on an array or iterable.
Also, the rest of the code would be appreciated as I have no idea what any of those referenced classes (Entry, BlockListener, etc.) look like.

 

@pie_flavor I need to use a while loop so I can delete the entry from the Hashmap while looping. The Entry Object is from Java itself, the BlockListener.getBrokenBlocks() is a new HashMap<Location, Material>();. I hope that helps!

 

@Smootey

Code:

for (Location loc : BlockListener.getBrokenBlocks().keySet()) {
    Material m = BlockListener.getBrokenBlocks().get(loc);
    //derp de derp derp durr
    BlockListener.getBrokenBlocks().remove(loc);
}

 

@pie_flavor If you would've tested it, you would've noticed, that this is not working, because you can't delete an Entry while looping the Hashmap.

Edit: Got it working by myself - just do

Code:

it.remove();

 

@Smootey Got it. You can actually delete an entry while looping.
What you can't do is delete an entry inside a subthread, i.e. BukkitRunnable.