Fixes #473, catches outdated player names and checks if all entries are UUIDs before converted and thus prevents the server crashing.

Split off logic into single responsibilities for storing, initializing and matching the UUID mappings. Added JUnit to create tests for the UUID Matcher to see if its legit. It tests against simple problems like unconform UUIDs and also tests against a valid UUID.

src/main/java/appeng/core/PlayerMappings.java

@@ -0,0 +1,79 @@
+/*
+ * This file is part of Applied Energistics 2.
+ * Copyright (c) 2013 - 2014, AlgorithmX2, All rights reserved.
+ *
+ * Applied Energistics 2 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Applied Energistics 2 is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
+ */
+
+package appeng.core;
+
+
+import java.util.Map;
+import java.util.UUID;
+
+import net.minecraftforge.common.config.ConfigCategory;
+
+import cpw.mods.fml.relauncher.FMLRelaunchLog;
+
+import com.google.common.base.Optional;
+
+
+/**
+ * Wrapper class for the player mappings.
+ * Will grant access to a pre initialized player map
+ * based on the "players" category in the settings.cfg
+ */
+public class PlayerMappings
+{
+	/**
+	 * View of player mappings, is not immutable,
+	 * since it needs to be edited upon runtime,
+	 * cause new players can join
+	 */
+	private final Map<Integer, UUID> mappings;
+
+	public PlayerMappings( ConfigCategory category, FMLRelaunchLog log )
+	{
+		final PlayerMappingsInitializer init = new PlayerMappingsInitializer( category, log );
+
+		this.mappings = init.getPlayerMappings();
+	}
+
+	/**
+	 * Tries to retrieve the UUID of a player.
+	 * Might not be stored inside of the map.
+	 * Should not happen though.
+	 *
+	 * @param id ID of the to be searched player
+	 *
+	 * @return maybe the UUID of the searched player
+	 */
+	public Optional<UUID> get( int id )
+	{
+		final UUID maybe = this.mappings.get( id );
+
+		return Optional.fromNullable( maybe );
+	}
+
+	/**
+	 * Put in new players when they join the server
+	 *
+	 * @param id   id of new player
+	 * @param uuid UUID of new player
+	 */
+	public void put( int id, UUID uuid )
+	{
+		this.mappings.put( id, uuid );
+	}
+}