code

@EventHandler
    public void OnPlayerJoinWorldEvent(PlayerChangedWorldEvent event) {
        if (Bukkit.getServer().getWorld("boompvp") == event.getPlayer().getWorld()) {

            MongoClient mongoClient = MongoClients.create(new ConnectionString("URI")); //throws NoClassDef

            Bukkit.dispatchCommand(Bukkit.getServer().getConsoleSender(), "mv tp " + event.getPlayer().getDisplayName() + " boompvp");
            event.getPlayer().setBedSpawnLocation(new Location(Bukkit.getWorld("boompvp"), 11, 52, 0));
            .....