public class UserManager {

    private static final HashMap<UUID, User> users = new HashMap<>();

    public static void createUser(User user){
        UUID uuid = user.getUuid();
        if(!users.containsKey(uuid)){
            users.put(uuid, user);
        }
    }

    public static User getUser(Player player){
        UUID uuid = player.getUniqueId();
        if(users.containsKey(uuid)){
            return users.get(uuid);
        }
        return users.getOrDefault(uuid, new User(player));
    }
}