Code: if(args[0].equalsIgnoreCase("list") && sender instanceof Player){ Player player = (Player) sender; if(player.hasPermission("Friends.add")){ List<String> list = plugin.getConfig().getStringList(player.getUniqueId().toString() + ".Friends"); player.sendMessage(ChatColor.BLUE + "You have " + list.size() + " friends."); for(int i = 0; i<list.size(); i++){ player.sendMessage(ChatColor.BLUE + ""+(i+1) + ". " + ChatColor.GREEN + plugin.api().UUIDToName(list.get(i))); } } } When i enter the command for this methods it works. But when i do it again it do not. Only works once. It said its something wrong with this on line 10. Code: public String UUIDToName(String uuid){ NameFetcher fetcher = new NameFetcher(Arrays.asList(UUID.fromString(uuid))); Map<UUID, String> response = null; try { response = fetcher.call(); } catch(Exception e){ plugin.getLogger().warning("Exception while running NameFetcher"); e.printStackTrace(); } String name = response.get(UUID.fromString(uuid)); return name; }