removing possibility of multible serverchanges at a time

src/main/java/eu/mhsl/craftattack/spawn/listener/PlayerDisconnectListener.java

@@ -0,0 +1,13 @@
+package eu.mhsl.craftattack.spawn.listener;
+
+import eu.mhsl.craftattack.spawn.util.PlayerOnlineUtil;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerQuitEvent;
+
+public class PlayerDisconnectListener implements Listener {
+    @EventHandler
+    public void onDisconnect(PlayerQuitEvent event) {
+        if (PlayerOnlineUtil.worldMuseumCheck(event.getPlayer())) PlayerOnlineUtil.remove(event.getPlayer());
+    }
+}

src/main/java/eu/mhsl/craftattack/spawn/listener/PlayerEntityInteractListener.java

@@ -1,8 +1,10 @@
 package eu.mhsl.craftattack.spawn.listener;
 
 import eu.mhsl.craftattack.spawn.util.ConfigUtil;
+import eu.mhsl.craftattack.spawn.util.PlayerOnlineUtil;
 import eu.mhsl.craftattack.spawn.util.PluginMessage;
 import eu.mhsl.craftattack.spawn.util.VillagerSpawner;
+import org.bukkit.Bukkit;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.Listener;
 import org.bukkit.event.player.PlayerInteractAtEntityEvent;
@@ -13,7 +15,11 @@ public class PlayerEntityInteractListener implements Listener {
     public void onInteract(PlayerInteractAtEntityEvent event) {
         if (!event.getRightClicked().equals(VillagerSpawner.getStaticVillager())) return;
         event.setCancelled(true);
+        if (PlayerOnlineUtil.worldMuseumCheck(event.getPlayer())) return;
+
         String servername = ConfigUtil.getConfigUtil().getConfig().getString("world-museum-name");
         pluginMessage.connect(event.getPlayer(), servername);
+        PlayerOnlineUtil.addPlayer(event.getPlayer());
+        Bukkit.getLogger().info(event.getPlayer().getName() + " connects to Worldmuseum");
     }
 }

src/main/java/eu/mhsl/craftattack/spawn/util/PlayerOnlineUtil.java

@@ -0,0 +1,20 @@
+package eu.mhsl.craftattack.spawn.util;
+
+import org.bukkit.entity.Player;
+import java.util.ArrayList;
+import java.util.List;
+
+public class PlayerOnlineUtil {
+    private static final List<Player> playerOnWorldMuseum= new ArrayList<>(); // if player is in list --> he will be connected to worldmuseum
+
+    public static void addPlayer(Player player) {
+        playerOnWorldMuseum.add(player);
+    }
+    public static boolean worldMuseumCheck(Player player) {
+        return playerOnWorldMuseum.contains(player);
+    }
+    public static void remove(Player player) {
+        playerOnWorldMuseum.remove(player);
+    }
+
+}

src/main/java/eu/mhsl/craftattack/spawn/util/VillagerSpawner.java

@@ -1,7 +1,6 @@
 package eu.mhsl.craftattack.spawn.util;
 
 import org.bukkit.Location;
-import org.bukkit.entity.Entity;
 import org.bukkit.entity.EntityType;
 import org.bukkit.entity.Villager;
 
@@ -12,9 +11,8 @@ public class VillagerSpawner {
         Location location = config.getVillagerLocation();
 
         assert EntityType.VILLAGER.getEntityClass() != null;
-        Entity entity = location.getWorld().spawn(location, EntityType.VILLAGER.getEntityClass());
+        Villager villager = (Villager) location.getWorld().spawn(location, EntityType.VILLAGER.getEntityClass());
 
-        Villager villager = (Villager) entity;
         villager.setAI(false);
         villager.setInvulnerable(true);
         villager.setSilent(true);