Make the forceOnePlayerNameCase much quicker and isolate it in an Engine class.

src/com/massivecraft/mcore/EngineOfflineCase.java

@@ -0,0 +1,131 @@
+package com.massivecraft.mcore;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerLoginEvent;
+import org.bukkit.event.player.PlayerLoginEvent.Result;
+
+import com.massivecraft.mcore.util.MUtil;
+import com.massivecraft.mcore.util.Txt;
+
+/**
+ * In minecraft a player name is case insensitive but has one and only one correct casing when written out.
+ * The correct casing is decided upon buying minecraft.
+ * If you register "Steve" noone else can register "stEvE".
+ * 
+ * If you then try to log in using "STEVE" in the minecraft launcher the name will be corrected to "Steve".
+ * This feature does however only work in online mode.
+ * 
+ * If you use a cracked client and an offline mode server you may log on to the server using both "Steve" and "STEVE".
+ * This cause unintended side effects. Some file systems (windows) are case insensitive and some (unix) are case sensitive.
+ * On Unix "Steve" and "STEVE" would have different inventories, locations etc. They would be considered different players.
+ * That would be confusing for the players.
+ * They would seem to lose their inventory when mistyping their name and this would only happen on some servers (those using unix). 
+ * 
+ * Additionally plugins may start acting weird if this rule is broken.
+ * 
+ * The purpose of this "engine" is to enforce the use of the one and same casing for offline mode servers.
+ * You "register" the correct casing at the first login.
+ * After that you get kicked when using an incorrect casing.
+ * 
+ */
+public class EngineOfflineCase implements Listener
+{
+	// -------------------------------------------- //
+	// INSTANCE & CONSTRUCT
+	// -------------------------------------------- //
+	
+	private static EngineOfflineCase i = new EngineOfflineCase();
+	public static EngineOfflineCase get() { return i; }
+	
+	// -------------------------------------------- //
+	// SETUP
+	// -------------------------------------------- //
+	
+	public void setup()
+	{
+		this.lowerToCorrect.clear();
+		
+		for (Player player : Bukkit.getOnlinePlayers())
+		{
+			this.registerCase(player.getName());
+		}
+		
+		for (String pdname : MUtil.getPlayerDirectoryNames())
+		{
+			this.registerCase(pdname);
+		}
+		
+		Bukkit.getPluginManager().registerEvents(this, MCore.get());
+	}
+	
+	// -------------------------------------------- //
+	// FIELDS
+	// -------------------------------------------- //
+	
+	private Map<String, String> lowerToCorrect = new HashMap<String, String>();
+	
+	// -------------------------------------------- //
+	// UTIL
+	// -------------------------------------------- //
+	
+	private void registerCase(String playerName)
+	{
+		this.lowerToCorrect.put(playerName.toLowerCase(), playerName);
+	}
+	
+	// -------------------------------------------- //
+	// LISTENER
+	// -------------------------------------------- //
+	
+	@EventHandler(priority = EventPriority.LOWEST)
+	public void forceOnePlayerNameCase(PlayerLoginEvent event)
+	{
+		// Stop if the feature is disabled
+		if (!ConfServer.forceOnePlayerNameCase) return;
+		
+		// Stop if we are using online mode
+		if (Bukkit.getOnlineMode()) return;
+		
+		// Prepare some variables
+		final Player player = event.getPlayer();
+		final String playerName = player.getName();
+		final String playerNameLower = playerName.toLowerCase();
+		
+		// Kick if the player already is online
+		// NOTE: Bukkit.getPlayerExact is case insensitive as it should be
+		final Player onlinePlayer = Bukkit.getPlayerExact(playerName);
+		if (onlinePlayer != null)
+		{
+			event.setResult(Result.KICK_OTHER);
+			event.setKickMessage(Txt.parse("<b>The player <h>%s <b>is already online.", onlinePlayer.getName()));
+			return;
+		}
+		
+		// Consider dat case!
+		String correct = this.lowerToCorrect.get(playerNameLower);
+		if (correct == null)
+		{
+			// "Register"
+			this.registerCase(playerName);
+		}
+		else
+		{
+			// Kick if the case is wrong
+			if (!correct.equals(playerName))
+			{
+				event.setResult(Result.KICK_OTHER);
+				event.setKickMessage(Txt.parse("<b>Invalid uppercase and lowercase letters in name.\n<i>Please spell this name like \"<h>%s<i>\".", correct));
+				return;
+			}
+		}
+		
+	}
+
+}

src/com/massivecraft/mcore/EngineWorldNameSet.java

@@ -12,14 +12,14 @@ import org.bukkit.event.Listener;
 import org.bukkit.event.world.WorldLoadEvent;
 import org.bukkit.event.world.WorldUnloadEvent;
 
-public class WorldNameSetEngine implements Listener
+public class EngineWorldNameSet implements Listener
 {
 	// -------------------------------------------- //
 	// INSTANCE & CONSTRUCT
 	// -------------------------------------------- //
 	
-	private static WorldNameSetEngine i = new WorldNameSetEngine();
-	public static WorldNameSetEngine get() { return i; }
+	private static EngineWorldNameSet i = new EngineWorldNameSet();
+	public static EngineWorldNameSet get() { return i; }
 	
 	// -------------------------------------------- //
 	// SETUP

src/com/massivecraft/mcore/InternalListener.java

@@ -31,10 +31,8 @@ import com.massivecraft.mcore.event.MCoreSenderUnregisterEvent;
 import com.massivecraft.mcore.mixin.Mixin;
 import com.massivecraft.mcore.store.Coll;
 import com.massivecraft.mcore.store.SenderColl;
-import com.massivecraft.mcore.util.MUtil;
 import com.massivecraft.mcore.util.SenderUtil;
 import com.massivecraft.mcore.util.SmokeUtil;
-import com.massivecraft.mcore.util.Txt;
 import com.massivecraft.mcore.wrap.PlayerConnectionWrapMCore;
 
 public class InternalListener implements Listener
@@ -56,44 +54,6 @@ public class InternalListener implements Listener
 		Bukkit.getPluginManager().registerEvents(this, MCore.get());
 	}
 	
-	// -------------------------------------------- //
-	// FORCE ONE PLAYER NAME CASE
-	// -------------------------------------------- //
-	// This is used with offline servers to prevent bugs on case sensitive file systems.
-	
-	@EventHandler(priority = EventPriority.LOWEST)
-	public void forceOnePlayerNameCase(PlayerLoginEvent event)
-	{
-		// If we are enforcing one player name case ...
-		if (!ConfServer.forceOnePlayerNameCase) return;
-		
-		// ... and the server is running in offline mode ...
-		if (Bukkit.getOnlineMode()) return;
-		
-		// ... prepare vars ...
-		Player player = event.getPlayer();
-		String playerName = player.getName();
-		
-		// ... is the player already online? ...
-		for (Player onlinePlayer: Bukkit.getOnlinePlayers())
-		{
-			if (!playerName.equalsIgnoreCase(onlinePlayer.getName())) continue;
-			event.setResult(Result.KICK_OTHER);
-			event.setKickMessage(Txt.parse("<b>The player <h>%s <b>is already online.", onlinePlayer.getName()));
-			return;
-		}
-		
-		// ... is the first found file name different?
-		for (String pdname : MUtil.getPlayerDirectoryNames())
-		{
-			if (!playerName.equalsIgnoreCase(pdname)) continue;
-			if (playerName.equals(pdname)) break;
-			event.setResult(Result.KICK_OTHER);
-			event.setKickMessage(Txt.parse("<b>Invalid uppercase and lowercase letters in name.\n<i>Please spell this name like \"<h>%s<i>\".", pdname));
-		}
-		
-	}
-	
 	// -------------------------------------------- //
 	// PLAYER CONNECTION WRAP INJECTION
 	// -------------------------------------------- //

src/com/massivecraft/mcore/MCore.java

@@ -142,7 +142,8 @@ public class MCore extends MPlugin
 		InternalListener.get().setup();
 		ScheduledTeleportEngine.get().setup();
 		TeleportMixinCauseEngine.get().setup();
-		WorldNameSetEngine.get().setup();
+		EngineWorldNameSet.get().setup();
+		EngineOfflineCase.get().setup();
 		
 		// Schedule the collection ticker.
 		Bukkit.getScheduler().scheduleSyncRepeatingTask(this, this.collTickTask, 1, 1);

src/com/massivecraft/mcore/util/MUtil.java

@@ -47,7 +47,7 @@ import org.bukkit.potion.PotionEffectType;
 
 import com.massivecraft.mcore.InternalListener;
 import com.massivecraft.mcore.MCore;
-import com.massivecraft.mcore.WorldNameSetEngine;
+import com.massivecraft.mcore.EngineWorldNameSet;
 import com.massivecraft.mcore.util.extractor.Extractor;
 import com.massivecraft.mcore.util.extractor.ExtractorMoneyUniverse;
 import com.massivecraft.mcore.util.extractor.ExtractorPlayer;
@@ -394,7 +394,7 @@ public class MUtil
 	
 	public static Set<String> getLoadedWorldNames()
 	{
-		return WorldNameSetEngine.get().getWorldNames();
+		return EngineWorldNameSet.get().getWorldNames();
 	}
 	
 	// -------------------------------------------- //