Minecraft Quizes

public class Quizes implements Listener {

    // Registers events
    public Quizes(<MainClass> mainClass) {
        Bukkit.getPluginManager().registerEvents(this, mainClass);
    }

    // Players current question
    public Map<UUID, Question> currentQuestion = new HashMap<>();

    // List of questions
    public List<Question> questions = new ArrayList<>();

    // Category index
    public Map<Integer, String> categories = new HashMap<>();

    // Generates questions
    public void setQuestions() {
        questions.add(new Question("You are playing minecraft.", true, "Newbie"));
        questions.add(new Question("Enderpearls teleport you to their location when thrown.", true, "Newbie"));

        questions.add(new Question("Sugar is needed to craft cake.", true, "Member"));
        questions.add(new Question("WorkBench's have a 3x3 crafting grid.", true, "Member"));
    }

    /*public Economy economy = null;
    public boolean setupEconomy() {
        RegisteredServiceProvider<Economy> economyProvider = Bukkit.getServer().getServicesManager().getRegistration(net.milkbowl.vault.economy.Economy.class);
        if (economyProvider != null) {
            economy = economyProvider.getProvider();
        }
        return (economy != null);
    }*/

    // Question object.
    // * Example: new Question(String, boolean, String)
    // * string - Question
    // * boolean - Answer
    // * string - Category
    public class Question {
        private String question;
        private boolean answer = true;
        private String category;
        private int index;

        public Question(String question, boolean answer, String category) {
            this.question = question;
            this.answer = answer;
            this.category = category;
            index = getNextIndex(this);

            if(!categories.values().contains(category.toLowerCase()))
                categories.put(categories.size()+1, category.toLowerCase());
        }

        public String getQuestion() {return question;}
        public boolean getAnswer() {return answer;}
        public String getCategory() {return category;}
        public int getIndex() {return index;}
    }

    // Retrieves the next index from provided category
    private int getNextIndex(Question question) {
        List<Question> questionsFromCategory = questions.stream().filter(q -> q.getCategory().equalsIgnoreCase(question.getCategory())).collect(Collectors.toList());
        return questionsFromCategory.size()+1;
    }

    // Retrieves first question from provided category
    private Question getFirstQuestion(String category) {
        return questions.stream().filter(q -> q.getCategory().equalsIgnoreCase(category) && q.getIndex() == 1).findAny().orElse(null);
    }

    // Retrieves next question from provided question
    private Question getNextQuestion(Question question) {
        String category = question.getCategory();
        int index = question.getIndex();

        return questions.stream().filter(q -> q.getCategory().equalsIgnoreCase(category) && q.getIndex() == (index+1)).findAny().orElse(null);
    }

    // Sends the player true and false message
    private void sendTrueAndFalse(Player p) {
        TextComponent[] text = {new TextComponent(Messages.util().addColor(" &7&l[&aTrue&7&l] ")), new TextComponent(Messages.util().addColor(" &7&l[&cFalse&7&l] "))};
        text[0].setClickEvent(new ClickEvent(ClickEvent.Action.RUN_COMMAND, "/answerquestion true"));
        text[1].setClickEvent(new ClickEvent(ClickEvent.Action.RUN_COMMAND, "/answerquestion false"));

        p.spigot().sendMessage(text[0], text[1]);
    }

    @EventHandler
    public void onInteract(PlayerInteractEvent e) {
        Player p = e.getPlayer();
        Block b = e.getClickedBlock();

        // Checks if questions is empty and runs method to add questions.
        if(questions.isEmpty()) setQuestions();

        if(b == null) return;
        if(!(b.getState() instanceof Sign)) return;

        Sign s = (Sign) b.getState();

        // Checks if sign is for quizes
        if(!ChatColor.stripColor(s.getLine(0)).equalsIgnoreCase("[quiz]")) return;

        // Checks is player has permission to break sign while sneaking
        if(p.isSneaking() && p.hasPermission("admin.permission.node")) return;

        // Checks if the player has already started a quiz
        if(currentQuestion.containsKey(p.getUniqueId())) return;
        e.setCancelled(true);

        String category = s.getLine(1).isEmpty() ? "Newbie" : ChatColor.stripColor(s.getLine(1));
        //double price = s.getLine(2).isEmpty() ? 0 : Double.valueOf(ChatColor.stripColor(s.getLine(2)));

        // Checks if player already has permission from the current category
        if(p.hasPermission("perm.node."+category)) return;

        /*if(price > 0) {
            if(economy == null)
                setupEconomy();

            if(!economy.getBalance(Bukkit.getOfflinePlayer(p.getUniqueId())) >= price) {
                p.sendMessage("Insufficient funds.");
                return;
            }else {
                economy.withdrawPlayer(Bukkit.getOfflinePlayer(p.getUniqueId()), price);
            }
        }*/

        /* Checks permissions from categories in order they were added
        for(int i = 1; i <= categories.size(); i++) {
            String cat = categories.get(i);
            if(p.hasPermission("perm.node."+cat) && i == categories.size())
                return;

            if(p.hasPermission("perm.node."+cat))
                continue;
            else
                break;
        }*/

        // Gets the first question from the category "newbie" or the category specified on line 2 of the sign
        Question q = getFirstQuestion(category);
        if(q == null) return;

        // Adds player to the currentQuestion map
        currentQuestion.put(p.getUniqueId(), q);

        p.sendMessage(q.getQuestion());
        sendTrueAndFalse(p);
    }

    @EventHandler
    public void onPreCommand(PlayerCommandPreprocessEvent event) {
        Player p = event.getPlayer();
        String command = event.getMessage();

        // Checks if command is our answer question command
        if(!command.startsWith("/answerquestion")) return;
        event.setCancelled(true);

        // Checks if the player is answering quiz questions
        if(!currentQuestion.containsKey(p.getUniqueId())) return;

        // Splits the command so we can get the answer the player chose
        String[] parse = command.split(" ");

        // Gets current question and answer from map using the players UUID
        Question current = currentQuestion.get(p.getUniqueId());
        boolean a = current.getAnswer();

        if(a == Boolean.valueOf(parse[1])) {
            // Player chose the correct answer for the question and the next question is being retrieved
            p.sendMessage("Correct!");
            Question next = getNextQuestion(current);
            if(next != null) {
                // A new question was found and is being sent to the player
                currentQuestion.put(p.getUniqueId(), next);
                p.sendMessage(next.getQuestion());
                sendTrueAndFalse(p);
            }else {
                // The end of the quiz was reached and the player is being removed from the quiz map
                p.sendMessage("Completed quiz from category "+current.getCategory());
                currentQuestion.remove(p.getUniqueId());
            }
        }else {
            p.sendMessage("Incorrect!");

            p.sendMessage("Go reclick the sign.");
            /*p.sendMessage(current.getQuestion());
            sendTrueAndFalse(p);*/

            currentQuestion.remove(p.getUniqueId());
        }
    }

    @EventHandler
    public void onQuit(PlayerQuitEvent event) {
        currentQuestion.remove(event.getPlayer().getUniqueId());
    }
}