// model/QuestionLibrary.java

public class QuestionLibrary {
    private int questionIndex;
    private ArrayList<Question> questions;

    public QuestionLibrary() {
        questionIndex = 0;
        createLibrary();
    }

    private void createLibrary() {
        Library library = LibraryFactory.createLibrary();
        questions = library.getLibrary();
    }

    public ArrayList<Question> getQuestions() {
        return questions;
    }

    public int getQuestionIndex() {
        return questionIndex;
    }

    public void updateQuestionIndex() {
        questionIndex = (questionIndex + 1) % questions.size();
    }

}

// model/LibraryFactory.java

public class LibraryFactory {
    public static Library createLibrary() {
        return new SocialLibrary();
    }
}

// model/Library.java

public interface Library {
    ArrayList<Question> getLibrary();
}

// model/SocialLibrary.java

public class SocialLibrary implements Library {
    public ArrayList<Question> getLibrary() {
        ArrayList<Question> questions = new ArrayList<Question>();
        Question question1 = new Question("Viet Nam co bao nhieu tinh thanh?", "62", "63", "64", "65", "b");
        Question question2 = new Question("Thanh pho cua tinh Phu Yen", "Nha Trang", "Quy Nhon", "Tuy Hoa",
                "Mu Cang Chai", "c");
        Question question3 = new Question("2018 la nam con gi?", "Cho", "Ga", "Bo", "Khi", "a");
        Question question4 = new Question("1+1=", "3", "4", "2", "Tat ca deu sai", "c");
        Question question5 = new Question("Ten game ban dang choi la gi?", "Find The Dog", "Find The Fish",
                "Find The Honey", "Honey The Find", "c");
        questions.add(question1);
        questions.add(question2);
        questions.add(question3);
        questions.add(question4);
        questions.add(question5);
        return questions;
    }
}