diff --git a/src/main/java/com/gmail/nossr50/util/blockmeta/BitSetChunkStore.java b/src/main/java/com/gmail/nossr50/util/blockmeta/BitSetChunkStore.java
index a1fe92e4b..2f4ffe9ce 100644
--- a/src/main/java/com/gmail/nossr50/util/blockmeta/BitSetChunkStore.java
+++ b/src/main/java/com/gmail/nossr50/util/blockmeta/BitSetChunkStore.java
@@ -2,6 +2,8 @@ package com.gmail.nossr50.util.blockmeta;
 
 import org.bukkit.Bukkit;
 import org.bukkit.World;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.*;
 import java.util.BitSet;
@@ -19,7 +21,7 @@ public class BitSetChunkStore implements ChunkStore, Serializable {
     private int worldHeight;
     private UUID worldUid;
 
-    public BitSetChunkStore(World world, int cx, int cz) {
+    public BitSetChunkStore(@NotNull World world, int cx, int cz) {
         this.cx = cx;
         this.cz = cz;
         this.worldUid = world.getUID();
@@ -50,7 +52,7 @@ public class BitSetChunkStore implements ChunkStore, Serializable {
     }
 
     @Override
-    public UUID getWorldId() {
+    public @NotNull UUID getWorldId() {
         return worldUid;
     }
 
@@ -153,7 +155,7 @@ public class BitSetChunkStore implements ChunkStore, Serializable {
         dirty = false;
     }
 
-    private static BitSetChunkStore deserialize(DataInputStream in) throws IOException {
+    private static BitSetChunkStore deserialize(@NotNull DataInputStream in) throws IOException {
         int magic = in.readInt();
         // Can be used to determine the format of the file
         int fileVersionNumber = in.readInt();
@@ -182,7 +184,7 @@ public class BitSetChunkStore implements ChunkStore, Serializable {
 
         public static final short STREAM_MAGIC = (short)0xACDC;
 
-        public static ChunkStore readChunkStore(DataInputStream inputStream) throws IOException {
+        public static @NotNull ChunkStore readChunkStore(DataInputStream inputStream) throws IOException {
             if (inputStream.markSupported())
                 inputStream.mark(2);
             short magicNumber = inputStream.readShort();
diff --git a/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManager.java b/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManager.java
index 5cb50ac7f..57c66a899 100644
--- a/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManager.java
+++ b/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManager.java
@@ -3,6 +3,7 @@ package com.gmail.nossr50.util.blockmeta;
 import org.bukkit.World;
 import org.bukkit.block.Block;
 import org.bukkit.block.BlockState;
+import org.jetbrains.annotations.Nullable;
 
 public interface ChunkManager {
     void closeAll();
@@ -14,7 +15,7 @@ public interface ChunkManager {
      * @param cz Chunk Z coordinate that is to be saved
      * @param world World that the Chunk is in
      */
-    void saveChunk(int cx, int cz, World world);
+    void saveChunk(int cx, int cz, @Nullable World world);
 
     /**
      * Informs the ChunkletManager a chunk is unloaded
@@ -23,7 +24,7 @@ public interface ChunkManager {
      * @param cz Chunk Z coordinate that is unloaded
      * @param world World that the chunk was unloaded in
      */
-    void chunkUnloaded(int cx, int cz, World world);
+    void chunkUnloaded(int cx, int cz, @Nullable World world);
 
     /**
      * Save all ChunkletStores related to the given world
@@ -53,7 +54,7 @@ public interface ChunkManager {
      * @param world World to check in
      * @return true if the given location is set to true, false if otherwise
      */
-    boolean isTrue(int x, int y, int z, World world);
+    boolean isTrue(int x, int y, int z, @Nullable World world);
 
     /**
      * Check to see if a given block location is set to true
@@ -61,7 +62,7 @@ public interface ChunkManager {
      * @param block Block location to check
      * @return true if the given block location is set to true, false if otherwise
      */
-    boolean isTrue(Block block);
+    boolean isTrue(@Nullable Block block);
 
     /**
      * Check to see if a given BlockState location is set to true
@@ -69,7 +70,7 @@ public interface ChunkManager {
      * @param blockState BlockState to check
      * @return true if the given BlockState location is set to true, false if otherwise
      */
-    boolean isTrue(BlockState blockState);
+    boolean isTrue(@Nullable BlockState blockState);
 
     /**
      * Set a given location to true, should create stores as necessary if the location does not exist
@@ -79,21 +80,21 @@ public interface ChunkManager {
      * @param z Z coordinate to set
      * @param world World to set in
      */
-    void setTrue(int x, int y, int z, World world);
+    void setTrue(int x, int y, int z, @Nullable World world);
 
     /**
      * Set a given block location to true, should create stores as necessary if the location does not exist
      *
      * @param block Block location to set
      */
-    void setTrue(Block block);
+    void setTrue(@Nullable Block block);
 
     /**
      * Set a given BlockState location to true, should create stores as necessary if the location does not exist
      *
      * @param blockState BlockState location to set
      */
-    void setTrue(BlockState blockState);
+    void setTrue(@Nullable BlockState blockState);
 
     /**
      * Set a given location to false, should not create stores if one does not exist for the given location
@@ -103,21 +104,21 @@ public interface ChunkManager {
      * @param z Z coordinate to set
      * @param world World to set in
      */
-    void setFalse(int x, int y, int z, World world);
+    void setFalse(int x, int y, int z, @Nullable World world);
 
     /**
      * Set a given block location to false, should not create stores if one does not exist for the given location
      *
      * @param block Block location to set
      */
-    void setFalse(Block block);
+    void setFalse(@Nullable Block block);
 
     /**
      * Set a given BlockState location to false, should not create stores if one does not exist for the given location
      *
      * @param blockState BlockState location to set
      */
-    void setFalse(BlockState blockState);
+    void setFalse(@Nullable BlockState blockState);
 
     /**
      * Delete any ChunkletStores that are empty
diff --git a/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManagerFactory.java b/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManagerFactory.java
index a290c5e2a..e2c47662e 100644
--- a/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManagerFactory.java
+++ b/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkManagerFactory.java
@@ -1,9 +1,10 @@
 package com.gmail.nossr50.util.blockmeta;
 
 import com.gmail.nossr50.config.HiddenConfig;
+import org.jetbrains.annotations.NotNull;
 
 public class ChunkManagerFactory {
-    public static ChunkManager getChunkManager() {
+    public static @NotNull ChunkManager getChunkManager() {
         HiddenConfig hConfig = HiddenConfig.getInstance();
 
         if (hConfig.getChunkletsEnabled()) {
diff --git a/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkStore.java b/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkStore.java
index eca783ccd..df01b93ee 100644
--- a/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkStore.java
+++ b/src/main/java/com/gmail/nossr50/util/blockmeta/ChunkStore.java
@@ -1,6 +1,7 @@
 package com.gmail.nossr50.util.blockmeta;
 
 import org.bukkit.World;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.UUID;
 
@@ -36,7 +37,7 @@ public interface ChunkStore {
      */
     int getChunkZ();
 
-    UUID getWorldId();
+    @NotNull UUID getWorldId();
 
     /**
      * Checks the value at the given coordinates
diff --git a/src/main/java/com/gmail/nossr50/util/blockmeta/HashChunkManager.java b/src/main/java/com/gmail/nossr50/util/blockmeta/HashChunkManager.java
index 888937872..f3023e0e3 100644
--- a/src/main/java/com/gmail/nossr50/util/blockmeta/HashChunkManager.java
+++ b/src/main/java/com/gmail/nossr50/util/blockmeta/HashChunkManager.java
@@ -5,14 +5,16 @@ import org.bukkit.Bukkit;
 import org.bukkit.World;
 import org.bukkit.block.Block;
 import org.bukkit.block.BlockState;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.*;
 import java.util.*;
 
 public class HashChunkManager implements ChunkManager {
-    private final HashMap<CoordinateKey, McMMOSimpleRegionFile> regionMap = new HashMap<>(); // Tracks active regions
-    private final HashMap<CoordinateKey, HashSet<CoordinateKey>> chunkUsageMap = new HashMap<>(); // Tracks active chunks by region
-    private final HashMap<CoordinateKey, ChunkStore> chunkMap = new HashMap<>(); // Tracks active chunks
+    private final @NotNull HashMap<CoordinateKey, McMMOSimpleRegionFile> regionMap = new HashMap<>(); // Tracks active regions
+    private final @NotNull HashMap<CoordinateKey, HashSet<CoordinateKey>> chunkUsageMap = new HashMap<>(); // Tracks active chunks by region
+    private final @NotNull HashMap<CoordinateKey, ChunkStore> chunkMap = new HashMap<>(); // Tracks active chunks
 
     @Override
     public synchronized void closeAll() {
@@ -32,7 +34,7 @@ public class HashChunkManager implements ChunkManager {
         regionMap.clear();
     }
 
-    private synchronized ChunkStore readChunkStore(World world, int cx, int cz) throws IOException {
+    private synchronized @Nullable ChunkStore readChunkStore(@NotNull World world, int cx, int cz) throws IOException {
         McMMOSimpleRegionFile rf = getSimpleRegionFile(world, cx, cz, false);
         if (rf == null)
             return null; // If there is no region file, there can't be a chunk
@@ -43,7 +45,7 @@ public class HashChunkManager implements ChunkManager {
         }
     }
 
-    private synchronized void writeChunkStore(World world, ChunkStore data) {
+    private synchronized void writeChunkStore(@NotNull World world, @NotNull ChunkStore data) {
         if (!data.isDirty())
             return; // Don't save unchanged data
         try {
@@ -58,7 +60,7 @@ public class HashChunkManager implements ChunkManager {
         }
     }
 
-    private synchronized McMMOSimpleRegionFile getSimpleRegionFile(World world, int cx, int cz, boolean createIfAbsent) {
+    private synchronized @Nullable McMMOSimpleRegionFile getSimpleRegionFile(World world, int cx, int cz, boolean createIfAbsent) {
         CoordinateKey regionKey = toRegionKey(world.getUID(), cx, cz);
 
         return regionMap.computeIfAbsent(regionKey, k -> {
@@ -73,7 +75,7 @@ public class HashChunkManager implements ChunkManager {
         });
     }
 
-    private ChunkStore loadChunk(int cx, int cz, World world) {
+    private @Nullable ChunkStore loadChunk(int cx, int cz, World world) {
         try {
             return readChunkStore(world, cx, cz);
         }
@@ -82,7 +84,7 @@ public class HashChunkManager implements ChunkManager {
         return null;
     }
 
-    private void unloadChunk(int cx, int cz, World world) {
+    private void unloadChunk(int cx, int cz, @NotNull World world) {
         CoordinateKey chunkKey = toChunkKey(world.getUID(), cx, cz);
         ChunkStore chunkStore = chunkMap.remove(chunkKey); // Remove from chunk map
         if (chunkStore == null)
@@ -102,7 +104,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void saveChunk(int cx, int cz, World world) {
+    public synchronized void saveChunk(int cx, int cz, @Nullable World world) {
         if (world == null)
             return;
 
@@ -120,7 +122,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void chunkUnloaded(int cx, int cz, World world) {
+    public synchronized void chunkUnloaded(int cx, int cz, @Nullable World world) {
         if (world == null)
             return;
 
@@ -128,7 +130,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void saveWorld(World world) {
+    public synchronized void saveWorld(@Nullable World world) {
         if (world == null)
             return;
 
@@ -148,7 +150,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void unloadWorld(World world) {
+    public synchronized void unloadWorld(@Nullable World world) {
         if (world == null)
             return;
 
@@ -185,7 +187,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized boolean isTrue(int x, int y, int z, World world) {
+    public synchronized boolean isTrue(int x, int y, int z, @Nullable World world) {
         if (world == null)
             return false;
 
@@ -214,7 +216,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized boolean isTrue(Block block) {
+    public synchronized boolean isTrue(@Nullable Block block) {
         if (block == null)
             return false;
 
@@ -222,7 +224,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized boolean isTrue(BlockState blockState) {
+    public synchronized boolean isTrue(@Nullable BlockState blockState) {
         if (blockState == null)
             return false;
 
@@ -230,12 +232,12 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void setTrue(int x, int y, int z, World world) {
+    public synchronized void setTrue(int x, int y, int z, @Nullable World world) {
         set(x, y, z, world, true);
     }
 
     @Override
-    public synchronized void setTrue(Block block) {
+    public synchronized void setTrue(@Nullable Block block) {
         if (block == null)
             return;
 
@@ -243,7 +245,7 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void setTrue(BlockState blockState) {
+    public synchronized void setTrue(@Nullable BlockState blockState) {
         if (blockState == null)
             return;
 
@@ -251,12 +253,12 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void setFalse(int x, int y, int z, World world) {
+    public synchronized void setFalse(int x, int y, int z, @Nullable World world) {
         set(x, y, z, world, false);
     }
 
     @Override
-    public synchronized void setFalse(Block block) {
+    public synchronized void setFalse(@Nullable Block block) {
         if (block == null)
             return;
 
@@ -264,14 +266,14 @@ public class HashChunkManager implements ChunkManager {
     }
 
     @Override
-    public synchronized void setFalse(BlockState blockState) {
+    public synchronized void setFalse(@Nullable BlockState blockState) {
         if (blockState == null)
             return;
 
         setFalse(blockState.getX(), blockState.getY(), blockState.getZ(), blockState.getWorld());
     }
 
-    public synchronized  void set(int x, int y, int z, World world, boolean value){
+    public synchronized void set(int x, int y, int z, @Nullable World world, boolean value){
         if (world == null)
             return;
 
@@ -307,15 +309,15 @@ public class HashChunkManager implements ChunkManager {
         cStore.set(ix, y, iz, value);
     }
 
-    private CoordinateKey blockCoordinateToChunkKey(UUID worldUid, int x, int y, int z) {
+    private CoordinateKey blockCoordinateToChunkKey(@NotNull UUID worldUid, int x, int y, int z) {
         return toChunkKey(worldUid, x >> 4, z >> 4);
     }
 
-    private CoordinateKey toChunkKey(UUID worldUid, int cx, int cz){
+    private CoordinateKey toChunkKey(@NotNull UUID worldUid, int cx, int cz){
         return new CoordinateKey(worldUid, cx, cz);
     }
 
-    private CoordinateKey toRegionKey(UUID worldUid, int cx, int cz) {
+    private CoordinateKey toRegionKey(@NotNull UUID worldUid, int cx, int cz) {
         // Compute region index (32x32 chunk regions)
         int rx = cx >> 5;
         int rz = cz >> 5;
@@ -323,11 +325,11 @@ public class HashChunkManager implements ChunkManager {
     }
 
     private static final class CoordinateKey {
-        public final UUID worldID;
+        public final @NotNull UUID worldID;
         public final int x;
         public final int z;
 
-        private CoordinateKey(UUID worldID, int x, int z) {
+        private CoordinateKey(@NotNull UUID worldID, int x, int z) {
             this.worldID = worldID;
             this.x = x;
             this.z = z;
diff --git a/src/main/java/com/gmail/nossr50/util/blockmeta/McMMOSimpleRegionFile.java b/src/main/java/com/gmail/nossr50/util/blockmeta/McMMOSimpleRegionFile.java
index bef730ff4..3f61c9bef 100644
--- a/src/main/java/com/gmail/nossr50/util/blockmeta/McMMOSimpleRegionFile.java
+++ b/src/main/java/com/gmail/nossr50/util/blockmeta/McMMOSimpleRegionFile.java
@@ -19,6 +19,9 @@
  */
 package com.gmail.nossr50.util.blockmeta;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
 import java.io.*;
 import java.util.BitSet;
 import java.util.zip.DeflaterOutputStream;
@@ -54,7 +57,7 @@ public class McMMOSimpleRegionFile {
     private final int segmentMask;
 
     // File location
-    private final File parent;
+    private final @NotNull File parent;
     // File access
     private final RandomAccessFile file;
 
@@ -62,7 +65,7 @@ public class McMMOSimpleRegionFile {
     private final int rx;
     private final int rz;
 
-    public McMMOSimpleRegionFile(File f, int rx, int rz) {
+    public McMMOSimpleRegionFile(@NotNull File f, int rx, int rz) {
         this.rx = rx;
         this.rz = rz;
         this.parent = f;
@@ -104,7 +107,7 @@ public class McMMOSimpleRegionFile {
         }
     }
 
-    public synchronized DataOutputStream getOutputStream(int x, int z) {
+    public synchronized @NotNull DataOutputStream getOutputStream(int x, int z) {
         int index = getChunkIndex(x, z); // Get chunk index
         return new DataOutputStream(new DeflaterOutputStream(new McMMOSimpleChunkBuffer(this, index)));
     }
@@ -144,7 +147,7 @@ public class McMMOSimpleRegionFile {
         file.writeInt(chunkNumBytes[index]);
     }
 
-    public synchronized DataInputStream getInputStream(int x, int z) throws IOException {
+    public synchronized @Nullable DataInputStream getInputStream(int x, int z) throws IOException {
         int index = getChunkIndex(x, z); // Get chunk index
         int byteLength = chunkNumBytes[index]; // Get byte length of data
 
diff --git a/src/test/java/ChunkStoreTest.java b/src/test/java/ChunkStoreTest.java
index f45b0e0c9..43f105bad 100644
--- a/src/test/java/ChunkStoreTest.java
+++ b/src/test/java/ChunkStoreTest.java
@@ -2,6 +2,7 @@ import com.gmail.nossr50.util.blockmeta.*;
 import com.google.common.io.Files;
 import org.bukkit.Bukkit;
 import org.bukkit.World;
+import org.jetbrains.annotations.NotNull;
 import org.junit.*;
 import org.junit.runner.RunWith;
 import org.mockito.Mockito;
@@ -227,7 +228,7 @@ public class ChunkStoreTest {
         }
 
         @Override
-        public UUID getWorldId() {
+        public @NotNull UUID getWorldId() {
             return worldUid;
         }