@Property
    @Persist(PersistenceConstants.FLASH)
    private Module module;

//...

    void onActivate() {
        if (module == null) module = new Module();
        if (module.getQuiz() == null) {
            module.setQuiz(new Quiz());
            for (int i = 0; i < answersNumber; i++) {
                module.getQuiz().getAnswersList().add(new QuizAnswer());
            }
        }
    }