Maybe better performance?

common/src/main/java/us/myles/ViaVersion/protocols/protocolsnapshotto1_12_2/packets/WorldPackets.java

@@ -248,18 +248,19 @@ public class WorldPackets {
     }
 
     public static int toNewId(int oldId) {
-        if (MappingData.oldToNewBlocks.containsKey(oldId)) {
-            return MappingData.oldToNewBlocks.get(oldId);
-        } else {
-            if (MappingData.oldToNewBlocks.containsKey((oldId >> 4) << 4)) {
+        Integer newId = MappingData.oldToNewBlocks.get(oldId);
+        if (newId != null) {
+            return newId;
+        }
+        newId = MappingData.oldToNewBlocks.get(oldId & ~0xF); // Remove data
+        if (newId != null) {
             System.out.println("Missing block " + oldId);
-                return MappingData.oldToNewBlocks.get((oldId >> 4) << 4);
+            return newId;
         }
         System.out.println("Missing block completely " + oldId);
         // Default stone
         return 1;
     }
-    }
 
     private static int checkStorage(UserConnection user, Position position, int newId) {
         BlockStorage storage = user.get(BlockStorage.class);

common/src/main/java/us/myles/ViaVersion/protocols/protocolsnapshotto1_12_2/storage/BlockStorage.java

@@ -1,19 +1,19 @@
 package us.myles.ViaVersion.protocols.protocolsnapshotto1_12_2.storage;
 
+import com.google.common.collect.Sets;
 import lombok.AllArgsConstructor;
 import lombok.Data;
 import us.myles.ViaVersion.api.data.StoredObject;
 import us.myles.ViaVersion.api.data.UserConnection;
 import us.myles.ViaVersion.api.minecraft.Position;
 
-import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.CopyOnWriteArrayList;
 
 public class BlockStorage extends StoredObject {
     // This BlockStorage is very exclusive (;
-    private static final List<Integer> whitelist = new CopyOnWriteArrayList<>();
+    private static final Set<Integer> whitelist = Sets.newConcurrentHashSet();
 
     static {
         // Flower pots