Plugin for poi

OnceWorldKits.java

package me.ultimate.OWK;

import java.util.ArrayList;
import java.util.List;

import org.bukkit.ChatColor;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerChangedWorldEvent;
import org.bukkit.event.player.PlayerQuitEvent;
import org.bukkit.plugin.java.JavaPlugin;

import com.lol768.LiteKits.API.KitCheckEvent;

public class OnceWorldKits extends JavaPlugin implements Listener {

   List<String> used = new ArrayList<String>();

   public void onEnable() {
      getServer().getPluginManager().registerEvents(this, this);
      if(!getConfig().isSet("Message")){
         getConfig().set("Message", "You have already used this kit in this world!");
      }
   }

   @EventHandler
   public void onKitCheck(KitCheckEvent event) {
      if (used.contains(event.getPlayer().getName())) {
         event.setCancelled(true);
         event.getPlayer().sendMessage(ChatColor.RED + getConfig().getString("Message", "You have already used this kit in this world!"));
      } else {
         used.add(event.getPlayer().getName());
      }
   }
   
   @EventHandler
   public void onPlayerChangeWorld(PlayerChangedWorldEvent event){
      if (used.contains(event.getPlayer().getName()))
         used.remove(event.getPlayer().getName());
   }

   @EventHandler
   public void onPlayerLogout(PlayerQuitEvent event) {
      if (used.contains(event.getPlayer().getName()))
         used.remove(event.getPlayer().getName());
   }

}