// model/QuestionLibrary.java
public class QuestionLibrary {
    private int questionIndex;
    private ArrayList<Question> questions;
    private QuestionList questionList;

    public QuestionLibrary() {
        questionList = new SocialQuestionList();
        initListQuestion();
    }

    private void initListQuestion() {
        questionIndex = 0;
        questions = questionList.createQuestionList();
    }

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

    public int getQuestionIndex() {
        return questionIndex;
    }

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

}
// model/QuestionList.java
public interface QuestionList {
    ArrayList<Question> createQuestionList();
}
// model/SocialQuestionList.java
public class SocialQuestionList implements QuestionList {

    @Override
    public ArrayList<Question> createQuestionList() {
        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;
    }
}