Concurrency update

src/engine/loot/WorkOrder.java

@@ -17,7 +17,7 @@ import java.time.Instant;
 import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.util.HashMap;
-import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Delayed;
 import java.util.concurrent.TimeUnit;
 
@@ -39,7 +39,7 @@ public class WorkOrder implements Delayed {
     public long completionTime;
     public boolean runCompleted = false;
     public boolean runCanceled = false;
-    public CopyOnWriteArrayList<Item> cooking = new CopyOnWriteArrayList<>();
+    public ConcurrentHashMap.KeySetView<Item, Boolean> cooking = ConcurrentHashMap.newKeySet();
 
     public WorkOrder() {