Anyone know why my hashmap manager is throwing this error

Here is a simple class controlling the addition, removal and displaying of a hashmap.
The hashmap holds ore blocks.

addOre is called when an ore is placed.
removeOre is called when an ore is removed.
printOres is called when an ore is placed and removed.

Code:java

public class OreManager {
 
    public static HashMap<String, String> ores = new HashMap<String, String>();
 
    public static void addOre(Location location, Material material){
        String loc = location.getBlockX() + "," + location.getBlockY() + "," + location.getBlockZ();
        ores.put(loc, material.name());
    }
 
    public static void removeOre(Location location, Material material){
        String loc = location.getBlockX() + "," + location.getBlockY() + "," + location.getBlockZ();
        for (String key : ores.keySet()){
            if (key.equals(loc)){
                ores.remove(key);
            }
        }
    }
 
    public static void printOres(Player player){
        for (String key : ores.keySet()){
            player.sendMessage(key + " --- " + ores.get(key));
        }
    }
 
}

Stack trace error: java.util.ConcurrentModificationException

Visually its a weird error. Placing ores always works. It's removing them that throws this error.
It seems to work when theres 1 or 2 ores in the hashmap, but any more throws this error.

Thanks

 

Concurrent modification exceptions happen when you're iterating over, and modifying the contents of, a collection or iterator at the same time.the for loop at 12 is iterating over the key set, and removing the ores a the same time.

 

Scullyking
You are removing keys from your hashmap while looping through it. Make a clone of the hashmap, remove keys from that, and set the original hashmap equal to the new cloned map.

Also, look into removing all your static identifiers as a side note.

Edit: Did not see your second post CorrieKay , ninja'd

 

CorrieKay AoH_Ruthless

Thanks a bunch!

 

Or just use an Iterator...