Ensure NameManager caches stay consistent with multiple threads accessing them

src/main/java/com/Acrobot/Breeze/Collection/SimpleCache.java

@@ -1,20 +1,21 @@
 package com.Acrobot.Breeze.Collection;
 
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 
 public class SimpleCache<K, V> {
-    private final LinkedHashMap<K, V> map;
+    private final Map<K, V> map;
 
     public SimpleCache(int cacheSize) {
-        map = new LinkedHashMap<K, V>(cacheSize * 10/9, 0.7f, true) {
+        map = Collections.synchronizedMap(new LinkedHashMap<K, V>(cacheSize * 10/9, 0.7f, true) {
             @Override
             protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
                 return size() > cacheSize;
             }
-        };
+        });
     }
 
     public V put(K key, V value) {

src/main/java/com/Acrobot/ChestShop/UUIDs/NameManager.java

@@ -36,6 +36,8 @@ import java.util.logging.Level;
  */
 @SuppressWarnings("UnusedAssignment") // I deliberately set the variables to null while initializing
 public class NameManager implements Listener {
+    private static final Object accountsLock = new Object();
+
     private static Dao<Account, String> accounts;
 
     private static SimpleCache<String, Account> usernameToAccount = new SimpleCache<>(Properties.CACHE_SIZE);
@@ -97,6 +99,7 @@ public class NameManager implements Listener {
      */
     public static Account getAccount(UUID uuid) {
         try {
+            synchronized (accountsLock) {
                 return uuidToAccount.get(uuid, () -> {
                     try {
                         Account account = accounts.queryBuilder().orderBy("lastSeen", false).where().eq("uuid", new SelectArg(uuid)).queryForFirst();
@@ -111,6 +114,7 @@ public class NameManager implements Listener {
                     }
                     throw new Exception("Could not find account for " + uuid);
                 });
+            }
         } catch (ExecutionException ignored) {
             return null;
         }
@@ -127,6 +131,7 @@ public class NameManager implements Listener {
         Preconditions.checkNotNull(fullName, "fullName cannot be null!");
         Preconditions.checkArgument(!fullName.isEmpty(), "fullName cannot be empty!");
         try {
+            synchronized (accountsLock) {
                 return usernameToAccount.get(fullName, () -> {
                     try {
                         Account account = accounts.queryBuilder().orderBy("lastSeen", false).where().eq("name", new SelectArg(fullName)).queryForFirst();
@@ -140,6 +145,7 @@ public class NameManager implements Listener {
                     }
                     throw new Exception("Could not find account for " + fullName);
                 });
+            }
         } catch (ExecutionException ignored) {
             return null;
         }
@@ -167,6 +173,7 @@ public class NameManager implements Listener {
         Account account = null;
 
         try {
+            synchronized (accountsLock) {
                 account = shortToAccount.get(shortName, () -> {
                     try {
                         Account a = accounts.queryBuilder().where().eq("shortName", new SelectArg(shortName)).queryForFirst();
@@ -179,6 +186,7 @@ public class NameManager implements Listener {
                     }
                     throw new Exception("Could not find account for " + shortName);
                 });
+            }
         } catch (ExecutionException ignored) {}
         return account;
     }
@@ -222,6 +230,7 @@ public class NameManager implements Listener {
         final UUID uuid = player.getUniqueId();
 
         Account latestAccount = null;
+        synchronized (accountsLock) {
             try {
                 latestAccount = accounts.queryBuilder().where().eq("uuid", new SelectArg(uuid)).and().eq("name", new SelectArg(player.getName())).queryForFirst();
             } catch (SQLException e) {
@@ -243,6 +252,7 @@ public class NameManager implements Listener {
             usernameToAccount.put(latestAccount.getName(), latestAccount);
             uuidToAccount.put(uuid, latestAccount);
             shortToAccount.put(latestAccount.getShortName(), latestAccount);
+        }
 
         return latestAccount;
     }