Reworked thread safe cache solution.

Also performed refactoring.

And added some threaded tests.

.vscode/launch.json

@@ -4,6 +4,13 @@
     // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
     "version": "0.2.0",
     "configurations": [
+        {
+            "type": "java",
+            "name": "CodeLens (Launch) - UniBiomeIslandGeneratorTest",
+            "request": "launch",
+            "mainClass": "ca.recrown.islandsurvivalcraft.world.generation.UniBiomeIslandGeneratorTest",
+            "projectName": "IslandSurvivalCraft"
+        },
         {
             "type": "java",
             "name": "Debug (Launch) - Current File",
@@ -16,7 +23,9 @@
             "request": "attach",
             "hostName": "localhost",
             "port": 25566,
-            "sourcePaths": ["src/main/java"],
+            "sourcePaths": [
+                "src/main/java"
+            ],
             "preLaunchTask": "start test server",
             "postDebugTask": "stop test server"
         }

pom.xml

@@ -11,9 +11,15 @@
     <repository>
       <id>papermc</id>
       <url>https://papermc.io/repo/repository/maven-public/</url>
-  </repository>
+    </repository>
   </repositories>
   <dependencies>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-api</artifactId>
+      <version>5.6.2</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>org.junit.jupiter</groupId>
       <artifactId>junit-jupiter-engine</artifactId>
@@ -25,7 +31,7 @@
       <artifactId>paper-api</artifactId>
       <version>1.15.2-R0.1-SNAPSHOT</version>
       <scope>provided</scope>
-   </dependency>
+    </dependency>
   </dependencies>
   <build>
     <plugins>
@@ -41,6 +47,10 @@
         <artifactId>maven-surefire-plugin</artifactId>
         <version>2.22.2</version>
       </plugin>
+      <plugin>
+          <artifactId>maven-failsafe-plugin</artifactId>
+          <version>2.22.2</version>
+      </plugin>
     </plugins>
   </build>
   <properties>

src/main/java/ca/recrown/islandsurvivalcraft/IslandSurvivalCraft.java

@@ -11,6 +11,7 @@ public class IslandSurvivalCraft extends JavaPlugin {
 
     @Override
     public void onEnable() {
+        
         super.onEnable();
     }
 

src/main/java/ca/recrown/islandsurvivalcraft/Utilities.java

@@ -4,7 +4,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Map.Entry;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 
 public class Utilities {
     public final static int CHUNK_SIZE = 16;

src/main/java/ca/recrown/islandsurvivalcraft/caching/Cache.java

@@ -1,22 +1,20 @@
 package ca.recrown.islandsurvivalcraft.caching;
 
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
 
-public class Cache<Key, Value> {
+public class Cache<K, V> {
     private final int maxSize;
-    private final ConcurrentHashMap<Key, CacheValue<Value>> data;
-    private final ConcurrentLinkedQueue<Key> occurrenceOrder;
-    private ReentrantReadWriteLock cleaningLock = new ReentrantReadWriteLock(true);
-    private WriteLock writeLock = cleaningLock.writeLock();
-    private ReadLock readLock = cleaningLock.readLock();
+    private final ConcurrentHashMap<K, CacheValue<K, V>> data;
+    private final UsageStack<K, V> usage = new UsageStack<>();
+    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+    private final WriteLock writeLock = lock.writeLock();
+    private final ReadLock readLock = lock.readLock();
 
     public Cache(int maxSize) {
         data = new ConcurrentHashMap<>(maxSize + 1, 0.75f, 6);
-        occurrenceOrder = new ConcurrentLinkedQueue<>();
         this.maxSize = maxSize;
     }
 
@@ -24,29 +22,23 @@ public class Cache<Key, Value> {
         this(1024);
     }
 
-    public void setValue(Key key, Value value) {
-        CacheValue<Value> previous = data.get(key);
-        CacheValue<Value> fresh = new CacheValue<>(value);
-        if (previous != null) fresh.occurrence += previous.occurrence;
-        occurrenceOrder.add(key);
-        data.put(key, fresh);
-
-        if (data.size() > maxSize) {
-            int occ = 0;
-            do {
-                Key potentialKey = occurrenceOrder.poll();
-                CacheValue<Value> potential = data.get(potentialKey);
-                potential.occurrence--;
-                writeLock.lock();
-                try {
-                    occ = potential.occurrence;
-                    if (occ < 1) {
-                        data.remove(potentialKey);
-                    } 
-                } finally {
-                    writeLock.unlock();
+    public void set(K key, V value) {
+        writeLock.lock();
+        try {
+            if (data.containsKey(key)) {
+                data.get(key).value = value;
+            } else {
+                CacheValue<K, V> val = new CacheValue<>();
+                val.key = key;
+                val.value = value;
+                data.put(key, val);
+                usage.add(val);
+                if (data.size() > maxSize) {
+                    data.remove(usage.pop().key);
                 }
-            } while (occ > 0);
+            }
+        } finally {
+            writeLock.unlock();
         }
     }
 
@@ -57,22 +49,26 @@ public class Cache<Key, Value> {
      * @param key the key associated with the value.
      * @return the value associated to the key.
      */
-    public Value getValue(Key key) {
-        CacheValue<Value> res = null;
+    public V get(K key) {
         readLock.lock();
+        CacheValue<K, V> value = null;
         try {
-            res = data.get(key);
-            if (res == null) return null;
-            res.occurrence++;
-            occurrenceOrder.add(key);
+            if (!data.containsKey(key)) return null;
+            value = data.get(key);
+            usage.tryMoveToTop(value);
         } finally {
             readLock.unlock();
         }
-        return res.data;
+        return value.value;
     }
 
     public void clearCache() {
-        data.clear();
-        occurrenceOrder.clear();
+        writeLock.lock();
+        try {
+            data.clear();
+            usage.clear();
+        } finally {
+            writeLock.unlock();
+        }
     }
 }

src/main/java/ca/recrown/islandsurvivalcraft/caching/CacheValue.java

@@ -1,10 +1,7 @@
 package ca.recrown.islandsurvivalcraft.caching;
 
-class CacheValue<ValueType> {
-    public volatile int occurrence = 1;
-    public final ValueType data;
-
-    public CacheValue(ValueType value) {
-        this.data = value;
-    }
+class CacheValue<KeyType, ValueType> {
+    public volatile KeyType key;
+    public volatile ValueType value;
+    public volatile CacheValue<KeyType, ValueType> front, back;
 }

src/main/java/ca/recrown/islandsurvivalcraft/caching/UsageStack.java

@@ -0,0 +1,89 @@
+package ca.recrown.islandsurvivalcraft.caching;
+
+import java.util.concurrent.locks.ReentrantLock;
+
+public class UsageStack<K, V> {
+    private volatile CacheValue<K, V> first, last;
+    private final ReentrantLock lock = new ReentrantLock();
+
+    private void addToTop(CacheValue<K, V> value) {
+        if (first != null) {
+            first.front = value;
+            value.back = first;
+        } else {
+            last = value;
+        }
+        value.front = null;
+        first = value;
+    }
+
+    private void removeValue(CacheValue<K, V> value) {
+        if (value.front != null) {
+            value.front.back = value.back;
+        } else {
+            first = value.back;
+        }
+        if (value.back != null) {
+            value.back.front = value.front;
+        } else {
+            last = value.front;
+        }
+        value.front = null;
+        value.back = null;
+    }
+
+    public void moveToTop(CacheValue<K, V> value) {
+        lock.lock();
+        try {
+            removeValue(value);
+            addToTop(value);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public boolean tryMoveToTop(CacheValue<K, V> value) {
+        boolean success = false;
+        success = lock.tryLock();
+        if (success) {
+            try {
+                removeValue(value);
+                addToTop(value);
+            } finally {
+                lock.unlock();
+            }
+        }
+        return success;
+    }
+
+    public void add(CacheValue<K, V> value) {
+        lock.lock();
+        try {
+            addToTop(value);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public CacheValue<K, V> pop() {
+        CacheValue<K, V> cacheValue;
+        lock.lock();
+        try {
+            cacheValue = last;
+            removeValue(last);
+        } finally {
+            lock.unlock();
+        }
+        return cacheValue;
+    }
+
+    public void clear() {
+        lock.lock();
+        try {
+            first = null;
+            last = null;
+        } finally {
+            lock.unlock();
+        }
+    }
+}

src/main/java/ca/recrown/islandsurvivalcraft/datatypes/Point2.java

@@ -1,4 +1,4 @@
-package ca.recrown.islandsurvivalcraft.types;
+package ca.recrown.islandsurvivalcraft.datatypes;
 
 import java.util.Objects;
 

src/main/java/ca/recrown/islandsurvivalcraft/floodfill/Floodable.java

@@ -1,6 +1,6 @@
 package ca.recrown.islandsurvivalcraft.floodfill;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 
 public interface Floodable {
     /**

src/main/java/ca/recrown/islandsurvivalcraft/floodfill/Flooder.java

@@ -3,7 +3,7 @@ package ca.recrown.islandsurvivalcraft.floodfill;
 import java.util.HashSet;
 import java.util.LinkedList;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 
 public class Flooder {
     private final Point2 start;

src/main/java/ca/recrown/islandsurvivalcraft/pathfinding/DFSNode.java

@@ -2,7 +2,7 @@ package ca.recrown.islandsurvivalcraft.pathfinding;
 
 import java.util.Objects;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 
 public class DFSNode extends Point2 implements Comparable<DFSNode> {
     private DFSNode goal;

src/main/java/ca/recrown/islandsurvivalcraft/pathfinding/DepthFirstSearch.java

@@ -6,7 +6,7 @@ import java.util.Queue;
 
 import org.apache.commons.lang.NullArgumentException;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 
 public class DepthFirstSearch {
     private Queue<DFSNode> queue;

src/main/java/ca/recrown/islandsurvivalcraft/world/IslandWorldMapper.java

@@ -4,7 +4,7 @@ import java.util.Random;
 
 import org.bukkit.util.noise.SimplexOctaveGenerator;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 import ca.recrown.islandsurvivalcraft.caching.Cache;
 import ca.recrown.islandsurvivalcraft.pathfinding.CoordinateValidatable;
 import ca.recrown.islandsurvivalcraft.pathfinding.DepthFirstSearch;
@@ -24,11 +24,11 @@ public class IslandWorldMapper implements CoordinateValidatable {
     private final float shallowPortion = 0.015f;
     private final DepthFirstSearch dfs;
 
-    public IslandWorldMapper(Random random) {
+    public IslandWorldMapper(Random random, Cache<Point2, Double> blockValueCache) {
         dfs = new DepthFirstSearch(this);
         this.noiseGenerator = new SimplexOctaveGenerator(random, noiseOctaves);
         noiseGenerator.setScale(scale);
-        blockValueCache = new Cache<>(65536);
+        this.blockValueCache = blockValueCache;
     }
     
     /**
@@ -114,7 +114,7 @@ public class IslandWorldMapper implements CoordinateValidatable {
     public double getWorldBlockValue(int worldX, int worldZ) {
         Point2 p = new Point2(worldX, worldZ);
 
-        Double res = blockValueCache.getValue(p);
+        Double res = blockValueCache.get(p);
         if (res == null) {
             double portionSea = 1f - (this.islandBlockGenerationPercent / 100f);
             double shift = 1f - 2 * portionSea;
@@ -133,7 +133,7 @@ public class IslandWorldMapper implements CoordinateValidatable {
             } else {
                 res = noise / maxPos;
             }
-            blockValueCache.setValue(p, res);
+            blockValueCache.set(p, res);
             return res;
         }
 

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/BiomeGenerator.java

@@ -3,6 +3,8 @@ package ca.recrown.islandsurvivalcraft.world.generation;
 import org.bukkit.World;
 import org.bukkit.block.Biome;
 
+import ca.recrown.islandsurvivalcraft.caching.Cache;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 import ca.recrown.islandsurvivalcraft.world.BiomeSelector;
 import ca.recrown.islandsurvivalcraft.world.IslandWorldMapper;
 
@@ -13,6 +15,7 @@ public interface BiomeGenerator {
      * The array should store the columns of biomes for the entire chunk.
      * It doesn't need to be populated on the first call as this method will be called once for every column in the chunk.
      * However, if some biomes can be set without repetative calls, doing so will prevent this method from being called for those locals.
+     * 
      * @param biomesArray The array of biomes that are to be saturated.
      * @param world The current world.
      * @param chunkX The X coordinate of the chunk.
@@ -21,13 +24,8 @@ public interface BiomeGenerator {
      * @param localZ The Z coordinate of the column within the chunk.
      * @param mapper The island mapper to be used.
      * @param tempGenerator The temperature generator to be used.
+     * @param biomeCache Cache for biomes.
+     * @param chunkGenCache Cache for whether or not the chunk is generated.
      */
-    public void generateBiomeColumn(Biome[][] biomesArray, World world, int chunkX, int chunkZ, int localX, int localZ, IslandWorldMapper mapper, BiomeSelector biomeSelector, TemperatureMapGenerator tempGenerator);
-
-    /**
-     * Called when Bukkit designates a new chunk as generated.
-     * @param chunkX The X coordinate of the chunk.
-     * @param chunkZ The Z coordinate of the chunk.
-     */
-    public void chunkGenerated(int chunkX, int chunkZ);
+    public void generateBiomeColumn(Biome[][] biomesArray, World world, int chunkX, int chunkZ, int localX, int localZ, IslandWorldMapper mapper, BiomeSelector biomeSelector, TemperatureMapGenerator tempGenerator, Cache<Point2, Biome> biomeCache, Cache<Point2, Boolean> chunkGenCache);
 }

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/IslandWorldChunkGenerator.java

@@ -7,43 +7,34 @@ import org.bukkit.Material;
 import org.bukkit.World;
 import org.bukkit.block.Biome;
 import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
 import org.bukkit.event.Listener;
 import org.bukkit.event.world.ChunkLoadEvent;
 import org.bukkit.generator.ChunkGenerator;
 
 import ca.recrown.islandsurvivalcraft.Utilities;
+import ca.recrown.islandsurvivalcraft.caching.Cache;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 import ca.recrown.islandsurvivalcraft.world.BiomeSelector;
 import ca.recrown.islandsurvivalcraft.world.IslandWorldMapper;
 import ca.recrown.islandsurvivalcraft.world.shaders.WorldHeightShader;
 
 public class IslandWorldChunkGenerator extends ChunkGenerator implements Listener {
-    private final BiomeGenerator biomeGenerator;
-    private final TemperatureMapGenerator temperatureGenerator = new TemperatureMapGenerator();
-    private volatile Random random;
-    private volatile IslandWorldMapper mapper;
-    private volatile BiomeSelector biomeSelector;
-    private volatile World world;
-    private volatile WorldHeightShader heightShader;
-
-    public IslandWorldChunkGenerator(BiomeGenerator biomeGenerator) {
-        this.biomeGenerator = biomeGenerator;
-    }
-
-    public IslandWorldChunkGenerator() {
-        this.biomeGenerator = new UniBiomeIslandGenerator();
-    }
+    private final Cache<Point2, Double> blockValueCache = new Cache<>(102400);
+    private final Cache<Point2, Biome> biomeCache = new Cache<>(102400);
+    private final Cache<Point2, Boolean> chunkExistenceCache = new Cache<>(16384);
+    private volatile World currentWorld;
 
     @Override
     public ChunkData generateChunkData(World world, Random random, int x, int z, BiomeGrid biome) {
-        if (this.random != random) {
-            this.random = random;
-            mapper = new IslandWorldMapper(random);
-            temperatureGenerator.setSeed(world.getSeed());
-            biomeSelector = new BiomeSelector(random);
-            biomeSelector.initialize();
-            this.world = world;
-            this.heightShader = new WorldHeightShader(world.getSeed(), mapper, world.getSeaLevel(), world.getMaxHeight(), 3);
-        }
+        this.currentWorld = world;
+        IslandWorldMapper mapper = new IslandWorldMapper(random, blockValueCache);
+        TemperatureMapGenerator temperatureMapGenerator = new TemperatureMapGenerator(world.getSeed());
+        BiomeSelector biomeSelector = new BiomeSelector(random);
+        biomeSelector.initialize();
+        WorldHeightShader heightShader = new WorldHeightShader(world.getSeed(), mapper, world.getSeaLevel(), world.getMaxHeight(), 3);
+        BiomeGenerator biomeGenerator = new UniBiomeIslandGenerator();
+
         int maxHeight = world.getMaxHeight();
         ChunkData chunkData = createChunkData(world);
 
@@ -51,7 +42,7 @@ public class IslandWorldChunkGenerator extends ChunkGenerator implements Listene
         for (int localX = 0; localX < Utilities.CHUNK_SIZE; localX++) {
             for (int localZ = 0; localZ < Utilities.CHUNK_SIZE; localZ++) {
                 if (biomes[localX][localZ] == null) {
-                    biomeGenerator.generateBiomeColumn(biomes, world, x, z, localX, localZ, mapper, biomeSelector, temperatureGenerator);
+                    biomeGenerator.generateBiomeColumn(biomes, world, x, z, localX, localZ, mapper, biomeSelector, temperatureMapGenerator, biomeCache, chunkExistenceCache);
                 }
                 if (biomes[localX][localZ] == null) throw new IllegalStateException("Biome was null.");
                 for (int y = 0; y < maxHeight; y++) {
@@ -68,12 +59,13 @@ public class IslandWorldChunkGenerator extends ChunkGenerator implements Listene
         return chunkData;
     }
 
-    @EventHandler
+    @EventHandler(priority = EventPriority.MONITOR)
     public void onChunkLoaded(ChunkLoadEvent event) {
         if (event.isNewChunk()) {
-            if (world == event.getWorld()) {
+            if (currentWorld == event.getWorld()) {
                 Chunk chunk = event.getChunk();
-                biomeGenerator.chunkGenerated(chunk.getX(), chunk.getZ());
+                
+                chunkExistenceCache.set(new Point2(chunk.getX(), chunk.getZ()), true);
             }
         }
     }

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/TemperatureMapGenerator.java

@@ -4,7 +4,7 @@ import java.util.Random;
 
 import org.bukkit.util.noise.SimplexOctaveGenerator;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 import ca.recrown.islandsurvivalcraft.caching.Cache;
 
 class TemperatureMapGenerator {
@@ -30,10 +30,10 @@ class TemperatureMapGenerator {
 
     public float getTemperature(int worldX, int worldZ) {
         Point2 loc = new Point2(worldX/4, worldZ/4);
-        Float val = temperatureCache.getValue(loc);
+        Float val = temperatureCache.get(loc);
         if (val == null) {
             val = (float) noiseGenerator.noise(worldX/4, worldZ/4, frequency, amplitude, true);
-            temperatureCache.setValue(loc, val);
+            temperatureCache.set(loc, val);
         }
         return val;
     }

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/UniBiomeIslandGenerator.java

@@ -4,27 +4,25 @@ import org.bukkit.World;
 import org.bukkit.block.Biome;
 
 import ca.recrown.islandsurvivalcraft.Utilities;
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 import ca.recrown.islandsurvivalcraft.caching.Cache;
+import ca.recrown.islandsurvivalcraft.floodfill.Floodable;
+import ca.recrown.islandsurvivalcraft.floodfill.Flooder;
 import ca.recrown.islandsurvivalcraft.pathfinding.CoordinateTargetValidatable;
-import ca.recrown.islandsurvivalcraft.pathfinding.CoordinateValidatable;
 import ca.recrown.islandsurvivalcraft.pathfinding.DepthFirstSearch;
 import ca.recrown.islandsurvivalcraft.world.BiomeSelector;
 import ca.recrown.islandsurvivalcraft.world.IslandWorldMapper;
 
 public class UniBiomeIslandGenerator implements BiomeGenerator {
-    private final Cache<Point2, Biome> biomeCache = new Cache<>(12800);
-    private final Cache<Point2, Boolean> existenceCache = new Cache<>(12800);
-
     @Override
-    public void generateBiomeColumn(Biome[][] biomes, World world, int chunkX, int chunkZ, int localX, int localZ, IslandWorldMapper mapper, BiomeSelector biomeSelector, TemperatureMapGenerator tempGen) {
+    public void generateBiomeColumn(Biome[][] biomes, World world, int chunkX, int chunkZ, int localX, int localZ, IslandWorldMapper mapper, BiomeSelector biomeSelector, TemperatureMapGenerator tempGen, Cache<Point2, Biome> biomeCache, Cache<Point2, Boolean> chunkGenCache) {
         int worldX = 16 * chunkX + localX;
         int worldZ = 16 * chunkZ + localZ;
         Point2 chunkCoords = Utilities.worldToChunkCoordinates(new Point2(worldX, worldZ));
-        existenceCache.setValue(chunkCoords, false);
+        chunkGenCache.set(chunkCoords, false);
 
         //Check if we can just give it something in cache.
-        Biome biome = getSavedBiome(world, worldX, worldZ);
+        Biome biome = getSavedBiome(world, worldX, worldZ, biomeCache, chunkGenCache);
         if (biome != null) {
             biomes[localX][localZ] = biome;
             return;
@@ -32,7 +30,7 @@ public class UniBiomeIslandGenerator implements BiomeGenerator {
 
         //Fine, check if it's ocean.
         if (!mapper.isIsland(worldX, worldZ)) {
-            setCacheBiome(worldX, worldZ, biomeSelector.getOceanBiome(tempGen.getTemperature(worldX, worldZ)), biomes);
+            setCacheBiome(worldX, worldZ, biomeSelector.getOceanBiome(tempGen.getTemperature(worldX, worldZ)), biomes, biomeCache);
             return;
         }
 
@@ -40,7 +38,7 @@ public class UniBiomeIslandGenerator implements BiomeGenerator {
         DepthFirstSearch search = new DepthFirstSearch();
         search.setValidatable(mapper);
         
-        IslandInfo islandInfo = new IslandInfo(mapper, world);
+        IslandInfo islandInfo = new IslandInfo(mapper, world, biomeCache, chunkGenCache);
         search.setStartPosition(worldX, worldZ);
         if (!search.findTarget(islandInfo)) {
             float temp = tempGen.getTemperature(worldX, worldZ);
@@ -49,105 +47,105 @@ public class UniBiomeIslandGenerator implements BiomeGenerator {
             if (islandInfo.shallow == null) islandInfo.shallow = biomeSelector.getOceanBiome(temp);
         }
 
-        PropagatorInfo propInfo = new PropagatorInfo(islandInfo, biomes, new Point2(chunkX, chunkZ), mapper);
-        search.setValidatable(propInfo);
-        search.setStartPosition(worldX, worldZ);
-        search.findTarget(propInfo);
+        PropagatorInfo propInfo = new PropagatorInfo(islandInfo, biomes, new Point2(chunkX, chunkZ), mapper, biomeCache);
+        Flooder flooder = new Flooder(new Point2(worldX, worldZ), propInfo);
+        flooder.start();
     }
 
-    private Biome getSavedBiome(World world, int worldX, int worldZ) {
+    private Biome getSavedBiome(World world, int worldX, int worldZ, Cache<Point2, Biome> biomeCache, Cache<Point2, Boolean> existenceCache) {
         Point2 worldCoords = new Point2(worldX, worldZ);
         Biome res = null;
 
 
-        res = biomeCache.getValue(worldCoords);
+        res = biomeCache.get(worldCoords);
         if (res != null) return res;
 
         Point2 chunkCoords = Utilities.worldToChunkCoordinates(worldCoords);
-        Boolean chunkExists = existenceCache.getValue(chunkCoords);
+        Boolean chunkExists = existenceCache.get(chunkCoords);
         if (chunkExists == null) {
             chunkExists = world.isChunkGenerated(worldX, worldZ);
-            existenceCache.setValue(chunkCoords, chunkExists);
+            existenceCache.set(chunkCoords, chunkExists);
         }
 
         if (chunkExists) {
             res = world.getBiome(worldX, 0, worldZ);
-            biomeCache.setValue(worldCoords, res);
+            biomeCache.set(worldCoords, res);
         }
         return res;
     }
 
-    public void chunkGenerated(int chunkX, int chunkZ) {
-        existenceCache.setValue(new Point2(chunkX, chunkZ), true);
-    }
-
-    private void setCacheBiome(int worldX, int worldZ, Biome biome, Biome[][] biomes) {
+    private void setCacheBiome(int worldX, int worldZ, Biome biome, Biome[][] localBiomes, Cache<Point2, Biome> biomeCache) {
         Point2 worldCoords = new Point2(worldX, worldZ);
-        if (biomes != null) {
+        if (localBiomes != null) {
             Point2 localCoords = Utilities.worldToLocalChunkCoordinates(worldCoords);
-            biomes[localCoords.x][localCoords.y] = biome;
+            localBiomes[localCoords.x][localCoords.y] = biome;
         }
-        biomeCache.setValue(worldCoords, biome);
+        biomeCache.set(worldCoords, biome);
     }
 
     private class IslandInfo implements CoordinateTargetValidatable {
         public final IslandWorldMapper mapper;
         public final World world;
+        private final Cache<Point2, Biome> biomeCache;
+        private final Cache<Point2, Boolean> chunkGenCache;
         public Biome main, shore, shallow;
         
-        public IslandInfo(IslandWorldMapper mapper, World world) {
+        public IslandInfo(IslandWorldMapper mapper, World world, Cache<Point2, Biome> biomeCache, Cache<Point2, Boolean> chunkGenCache) {
             this.mapper = mapper;
             this.world = world;
+            this.biomeCache = biomeCache;
+            this.chunkGenCache = chunkGenCache;
         }
 
         @Override
         public boolean isCoordinateTarget(int x, int y) {
             if (mapper.isLand(x, y)) {
                 if (mapper.isShore(x, y)) {
-                    shore = getSavedBiome(world, x, y);
+                    shore = getSavedBiome(world, x, y, biomeCache, chunkGenCache);
                 } else {
-                    main = getSavedBiome(world, x, y);
+                    main = getSavedBiome(world, x, y, biomeCache, chunkGenCache);
                 }
             } else {
-                shallow = getSavedBiome(world, x, y);
+                shallow = getSavedBiome(world, x, y, biomeCache, chunkGenCache);
             }
             return main != null && shore != null && shallow != null;
         }
     }
 
-    private class PropagatorInfo implements CoordinateTargetValidatable, CoordinateValidatable {
+    private class PropagatorInfo implements Floodable {
         private final Biome shallow, shore, main;
         private final Biome[][] biomes;
         private final Point2 chunkCoords;
         private final IslandWorldMapper mapper;
+        private final Cache<Point2, Biome> biomeCache;
 
-        public PropagatorInfo(IslandInfo islandInfo, Biome[][] biomes, Point2 chunkCoords, IslandWorldMapper mapper) {
+        public PropagatorInfo(IslandInfo islandInfo, Biome[][] biomes, Point2 chunkCoords, IslandWorldMapper mapper, Cache<Point2, Biome> biomeCache) {
             this.shallow = islandInfo.shallow;
             this.shore = islandInfo.shore;
             this.main = islandInfo.main;
             this.biomes = biomes;
             this.chunkCoords = chunkCoords;
             this.mapper = mapper;
+            this.biomeCache = biomeCache;
         }
 
         @Override
-        public boolean validate(int x, int y) {
-            Point2 chunkCoords = Utilities.worldToChunkCoordinates(new Point2(x, y));
-            return this.chunkCoords.fastEquals(chunkCoords) && mapper.validate(x, y);
-        }
-
-        @Override
-        public boolean isCoordinateTarget(int x, int y) {
+        public boolean flood(Point2 point) {
+            Point2 chunkCoords = Utilities.worldToChunkCoordinates(point);
+            if (!this.chunkCoords.fastEquals(chunkCoords) || !mapper.validate(point.x, point.y)) return false;
+            int x = point.x;
+            int y = point.y;
             if (mapper.isLand(x, y)) {
                 if (mapper.isShore(x, y)) {
-                    setCacheBiome(x, y, shore, biomes);
+                    setCacheBiome(x, y, shore, biomes, biomeCache);
                 } else {
-                    setCacheBiome(x, y, main, biomes);
+                    setCacheBiome(x, y, main, biomes, biomeCache);
                 }
             } else {
-                setCacheBiome(x, y, shallow, biomes);
+                setCacheBiome(x, y, shallow, biomes, biomeCache);
             }
-            return false;
+
+            return true;
         }
 
     }

src/test/java/ca/recrown/islandsurvivalcraft/UtilitiesTest.java

@@ -9,7 +9,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
 import org.junit.jupiter.api.TestInstance.Lifecycle;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 
 /**
  * Unit test for simple App.

src/test/java/ca/recrown/islandsurvivalcraft/caching/CacheTest.java

@@ -2,9 +2,14 @@ package ca.recrown.islandsurvivalcraft.caching;
 
 import static org.junit.Assert.assertSame;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.Random;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeAll;
@@ -28,35 +33,35 @@ public class CacheTest {
 
     @Test
     public void testBasicCaching() {
-        String val = integerCache.getValue(0);
+        String val = integerCache.get(0);
         assertTrue(val == null);
         val = "first";
-        integerCache.setValue(0, val);
-        assertTrue(integerCache.getValue(0) != null);
-        assertSame(val, integerCache.getValue(0));
+        integerCache.set(0, val);
+        assertTrue(integerCache.get(0) != null);
+        assertSame(val, integerCache.get(0));
 
-        val = integerCache.getValue(1);
+        val = integerCache.get(1);
         assertTrue(val == null);
         val = "second";
-        integerCache.setValue(1, val);
-        assertTrue(integerCache.getValue(1) != null);
-        assertSame(val, integerCache.getValue(1));
+        integerCache.set(1, val);
+        assertTrue(integerCache.get(1) != null);
+        assertSame(val, integerCache.get(1));
     }
 
     @Test
     public void testUsageBasedClean() {
-        integerCache.setValue(0, "first");
-        integerCache.setValue(1, "second");
-        integerCache.setValue(2, "third");
-        
-        assertEquals("first", integerCache.getValue(0));
+        integerCache.set(0, "first");
+        integerCache.set(1, "second");
+        integerCache.set(2, "third");
 
-        integerCache.setValue(3, "fourth");
-        assertEquals("first", integerCache.getValue(0));
+        assertEquals("first", integerCache.get(0));
 
-        integerCache.setValue(4, "fifth");
-        assertTrue(integerCache.getValue(3) != null);
-        assertTrue(integerCache.getValue(0) != null);
+        integerCache.set(3, "fourth");
+        assertEquals("first", integerCache.get(0));
+
+        integerCache.set(4, "fifth");
+        assertTrue(integerCache.get(3) != null);
+        assertTrue(integerCache.get(0) != null);
     }
 
     @Test
@@ -64,20 +69,20 @@ public class CacheTest {
         int amount = 1024;
         Random random = new Random();
 
-        Cache<Integer, Integer> largeCache = new Cache<>(amount/2);
+        Cache<Integer, Integer> largeCache = new Cache<>(amount / 2);
 
         int[] values = new int[amount];
         for (int i = 0; i < amount; i++) {
             values[i] = random.nextInt();
-            largeCache.setValue(i, values[i]);
+            largeCache.set(i, values[i]);
         }
 
-        for (int i = 0; i < amount /2; i++) {
-            assertEquals(null, largeCache.getValue(i), "Current accessor: " + i);
+        for (int i = 0; i < amount / 2; i++) {
+            assertEquals(null, largeCache.get(i), "Current accessor: " + i);
         }
 
-        for (int i = amount /2; i < amount; i++) {
-            assertEquals(values[i], largeCache.getValue(i), "Current accessor: " + i);
+        for (int i = amount / 2; i < amount; i++) {
+            assertEquals(values[i], largeCache.get(i), "Current accessor: " + i);
         }
     }
 
@@ -86,23 +91,194 @@ public class CacheTest {
         int amount = 1024;
         Random random = new Random();
 
-        Cache<Integer, Integer> largeCache = new Cache<>(amount/2);
+        Cache<Integer, Integer> largeCache = new Cache<>(amount / 2);
 
         int[] values = new int[amount];
         for (int i = 0; i < amount; i++) {
             values[i] = random.nextInt();
-            largeCache.setValue(i, values[i]);
-            largeCache.getValue(0);
+            largeCache.set(i, values[i]);
+            largeCache.get(0);
         }
 
-        for (int i = 1; i < (amount/2) + 1; i++) {
-            assertEquals(null, largeCache.getValue(i), "Current accessor: " + i);
+        for (int i = 1; i < (amount / 2) + 1; i++) {
+            assertEquals(null, largeCache.get(i), "Current accessor: " + i);
         }
 
-        for (int i = (amount /2) + 1; i < amount; i++) {
-            assertEquals(values[i], largeCache.getValue(i), "Current accessor: " + i);
+        for (int i = (amount / 2) + 1; i < amount; i++) {
+            assertEquals(values[i], largeCache.get(i), "Current accessor: " + i);
         }
 
-        assertEquals(values[0], largeCache.getValue(0));
+        assertEquals(values[0], largeCache.get(0));
+    }
+
+    @Test
+    public void testMultithreadingWriteConsistency() {
+        int size = 16384;
+        int[] answers = new int[size];
+        Random rand = new Random();
+
+        for (int i = 0; i < answers.length; i++) {
+            answers[i] = rand.nextInt();
+        }
+        Cache<Integer, Integer> lCache = new Cache<>(size);
+        Runnable write = new Runnable() {
+            @Override
+            public void run() {
+                for (int i = 0; i < size; i++) {
+                    lCache.set(i, answers[i]);
+                }
+            }
+        };
+
+        Thread firstThread = new Thread(write);
+        firstThread.start();
+        Thread secondThread = new Thread(write);
+        secondThread.start();
+        Thread thirdThread = new Thread(write);
+        thirdThread.start();
+
+        try {
+            firstThread.join();
+            secondThread.join();
+            thirdThread.join();
+        } catch (InterruptedException e) {
+            assertFalse(false, e.getCause().getMessage());
+        }
+
+        for (int i = 0; i < size; i++) {
+            assertEquals(answers[i], lCache.get(i), "Accessor at: " + i);
+        }
+    }
+
+    @Test
+    public void testMultithreadingReadConsistency() {
+        int size = 16384;
+        Cache<Integer, Integer> lCache = new Cache<>(size);
+        int[] answers = new int[size];
+        Random rand = new Random();
+
+        for (int i = 0; i < answers.length; i++) {
+            answers[i] = rand.nextInt();
+            lCache.set(i, answers[i]);
+        }
+
+        Runnable read = new Runnable() {
+            @Override
+            public void run() {
+                for (int i = 0; i < size; i++) {
+                    assertEquals(answers[i], lCache.get(i), "Accessor at: " + i);
+                }
+            }
+        };
+
+        Thread firstThread = new Thread(read);
+        firstThread.start();
+        Thread secondThread = new Thread(read);
+        secondThread.start();
+        Thread thirdThread = new Thread(read);
+        thirdThread.start();
+
+        try {
+            firstThread.join();
+            secondThread.join();
+            thirdThread.join();
+        } catch (InterruptedException e) {
+            assertFalse(false, e.getCause().getMessage());
+        }
+    }
+
+    @Test
+    public void testMulthreadedReadWrite() {
+        int size = 16384;
+        Cache<Integer, Integer> lCache = new Cache<>(size);
+        int[] answers = new int[size];
+        Random rand = new Random();
+
+        for (int i = 0; i < answers.length; i++) {
+            answers[i] = rand.nextInt();
+            lCache.set(i, answers[i]);
+        }
+
+        Runnable readWrite = new Runnable() {
+            @Override
+            public void run() {
+                for (int i = 0; i < size / 2; i++) {
+                    if (lCache.get(i) == null) {
+                        lCache.set(i, answers[i]);
+                    } else {
+                        assertEquals(answers[i], lCache.get(i), "Accessor at: " + i);
+                    }
+                }
+            }
+        };
+
+        Runnable readAll = new Runnable() {
+
+            @Override
+            public void run() {
+                for (int i = 0; i < size; i++) {
+                    assertEquals(answers[i], lCache.get(i), "Accessor at: " + i);
+                }
+            }
+        };
+
+        Thread firstThread = new Thread(readWrite);
+        firstThread.start();
+        Thread secondThread = new Thread(readWrite);
+        secondThread.start();
+        Thread thirdThread = new Thread(readAll);
+
+        try {
+            firstThread.join();
+            secondThread.join();
+            thirdThread.start();
+            thirdThread.join();
+        } catch (InterruptedException e) {
+            assertFalse(false, e.getCause().getMessage());
+        }
+    }
+
+    @Test
+    public void testMultiThreadConsistency() {
+        int size = 51200;
+        Cache<Integer, Integer> lCache = new Cache<>(size / 2);
+        int[] answers = new int[size];
+        Random rand = new Random();
+        ConcurrentHashMap<Integer, Integer> expectedStoredValues = new ConcurrentHashMap<>();
+
+        for (int i = 0; i < answers.length; i++) {
+            answers[i] = rand.nextInt();
+            lCache.set(i, answers[i]);
+        }
+
+        Runnable readWriteCheck = new Runnable(){
+        
+            @Override
+            public void run() {
+                for (int i = 0; i < size; i++) {
+                    if (lCache.get(i) != null) {
+                        assertEquals(answers[i], lCache.get(i), "Accessor at: " + i);
+                    } else {
+                        lCache.set(i, answers[i]);
+                        expectedStoredValues.put(i, answers[i]);
+                    }
+                }
+            }
+        };
+
+        ExecutorService executorService = Executors.newFixedThreadPool(6);
+        executorService.submit(readWriteCheck);
+        executorService.submit(readWriteCheck);
+        executorService.submit(readWriteCheck);
+        executorService.submit(readWriteCheck);
+        executorService.submit(readWriteCheck);
+        executorService.submit(readWriteCheck);
+
+        try {
+            executorService.shutdown();
+            assertTrue(executorService.awaitTermination(1, TimeUnit.MINUTES), "Timed out.");
+        } catch (InterruptedException e) {
+            assertFalse(false, e.getCause().getMessage());
+        }
     }
 }

src/test/java/ca/recrown/islandsurvivalcraft/floodfill/FloodFillTest.java

@@ -13,7 +13,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
 import org.junit.jupiter.api.TestInstance.Lifecycle;
 
-import ca.recrown.islandsurvivalcraft.types.Point2;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
 
 @TestInstance(Lifecycle.PER_CLASS)
 public class FloodFillTest {

src/test/java/ca/recrown/islandsurvivalcraft/world/generation/UniBiomeIslandGeneratorTest.java

@@ -0,0 +1,109 @@
+package ca.recrown.islandsurvivalcraft.world.generation;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import org.bukkit.block.Biome;
+import org.junit.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.api.TestInstance.Lifecycle;
+
+import ca.recrown.islandsurvivalcraft.Utilities;
+import ca.recrown.islandsurvivalcraft.caching.Cache;
+import ca.recrown.islandsurvivalcraft.datatypes.Point2;
+import ca.recrown.islandsurvivalcraft.world.BiomeSelector;
+import ca.recrown.islandsurvivalcraft.world.IslandWorldMapper;
+
+@TestInstance(Lifecycle.PER_CLASS)
+public class UniBiomeIslandGeneratorTest {
+    private final int SEED = 249398015;
+    private final DummyWorld dummyWorld = new DummyWorld();
+    private final Cache<Point2, Double> blockValueCache = new Cache<>(102400);
+    private final Cache<Point2, Biome> biomeCache = new Cache<>(102400);
+    private final Cache<Point2, Boolean> chunkExistenceCache = new Cache<>(16384);
+    private final Random rand = new Random(SEED);
+
+    private class BiomeGenTask implements Runnable {
+        private final int amount;
+        private final int shift;
+
+        public BiomeGenTask(int amount, int shift) {
+            this.shift = shift;
+            this.amount = amount;
+        }
+
+        @Override
+        public void run() {
+            for (int x = 0; x < amount; x++) {
+                generateBiome(x, shift);
+            }
+
+        }
+
+        public void generateBiome(int chunkX, int chunkZ) {
+            IslandWorldMapper mapper = new IslandWorldMapper(rand, blockValueCache);
+            TemperatureMapGenerator temperatureMapGenerator = new TemperatureMapGenerator(SEED);
+            BiomeSelector biomeSelector = new BiomeSelector(rand);
+            biomeSelector.initialize();
+            BiomeGenerator biomeGenerator = new UniBiomeIslandGenerator();
+
+            Biome[][] biomes = new Biome[Utilities.CHUNK_SIZE][Utilities.CHUNK_SIZE];
+            for (int localX = 0; localX < Utilities.CHUNK_SIZE; localX++) {
+                for (int localZ = 0; localZ < Utilities.CHUNK_SIZE; localZ++) {
+                    if (biomes[localX][localZ] == null) {
+                        biomeGenerator.generateBiomeColumn(biomes, dummyWorld, chunkX, chunkZ, localX, localZ, mapper,
+                                biomeSelector, temperatureMapGenerator, biomeCache, chunkExistenceCache);
+                    }
+                    if (biomes[localX][localZ] == null)
+                        throw new IllegalStateException("Biome was null.");
+                }
+            }
+        }
+    }
+
+    @Test
+    public void testBiomeGenerationMultithread() {
+        int chunksToDo = 280;
+        Runnable g1 = new BiomeGenTask(chunksToDo, 0);
+        Runnable g2 = new BiomeGenTask(chunksToDo, 1);
+        Runnable g3 = new BiomeGenTask(chunksToDo, 2);
+        Runnable g4 = new BiomeGenTask(chunksToDo, 3);
+        Runnable g5 = new BiomeGenTask(chunksToDo, 4);
+        Runnable g6 = new BiomeGenTask(chunksToDo, 5);
+
+        ExecutorService ex = Executors.newFixedThreadPool(6);
+        ex.execute(g1);
+        ex.execute(g2);
+        ex.execute(g3);
+        ex.execute(g4);
+        ex.execute(g5);
+        ex.execute(g6);
+
+        try {
+            ex.shutdown();
+            assertTrue(ex.awaitTermination(1, TimeUnit.MINUTES), "timed out.");
+        } catch (InterruptedException e) {
+            assertFalse(false);
+        }
+    }
+
+    @Test
+    public void testBiomeGenerationSingleThread() {
+        Runnable g1 = new BiomeGenTask(1680, 0);
+
+        ExecutorService ex = Executors.newFixedThreadPool(6);
+        ex.execute(g1);
+
+        try {
+            ex.shutdown();
+            assertTrue(ex.awaitTermination(1, TimeUnit.MINUTES));
+        } catch (InterruptedException e) {
+            assertFalse(false, e.getCause().getMessage());
+        }
+    }
+}