diff --git a/src/main/java/world/bentobox/level/calculators/CalcIslandLevel.java b/src/main/java/world/bentobox/level/calculators/CalcIslandLevel.java
index e64b31d..7bd747d 100644
--- a/src/main/java/world/bentobox/level/calculators/CalcIslandLevel.java
+++ b/src/main/java/world/bentobox/level/calculators/CalcIslandLevel.java
@@ -1,6 +1,16 @@
 package world.bentobox.level.calculators;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.EnumMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.Set;
+import java.util.UUID;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -38,7 +48,7 @@ public class CalcIslandLevel {
     private final Runnable onExit;
 
     // Copy the limits hash map
-    private final HashMap<Material, Integer> limitCount;
+    private final Map<Material, Integer> limitCount;
     private final List<World> worlds;
     private final World world;
 
@@ -59,7 +69,7 @@ public class CalcIslandLevel {
         this.addon = addon;
         this.island = island;
         this.world = island.getWorld();
-        this.limitCount = new HashMap<>(addon.getSettings().getBlockLimits());
+        this.limitCount = new EnumMap<>(addon.getSettings().getBlockLimits());
         this.onExit = onExit;
         this.worlds = new ArrayList<>();
         this.worlds.add(world);
@@ -93,6 +103,7 @@ public class CalcIslandLevel {
             }
         }
         queueid = Bukkit.getScheduler().scheduleSyncRepeatingTask(addon.getPlugin(), new Runnable() {
+            @Override
             public void run() {
                 for (int i = 0; i < 10; i++) {
                     if (q.size() == 0) {