java List与json的转换

/**
     * 根据页面用户输入的信息形成 Answer 对象的List
     *
     * @param answers
     * @param question_ids
     * @param types
     * @return
     */
    private List toAnswerList(String[] studenAnswers, int[] question_ids,
            int[] types,int[] scores) {
        List answerList = new ArrayList();

        if(studenAnswers!=null && question_ids!= null && types!= null&& scores!= null){
            for (int i = 0; i < studenAnswers.length; i++) {

                Answer answer = new Answer();
                String studenAnswer = studenAnswers[i];
                int type = types[i];
                int question_id = question_ids[i];
                int score = scores[i];


                answer.setQuestion_id(question_id);
                answer.setScore(score);
                answer.setStudenAnswer(studenAnswer);
                answer.setType(type);

                answerList.add(answer);
            }
        }
        return answerList;
    }

    /**
     * 将一个json字串转为list
     * @param props
     * @return
     */
    public static List converAnswerFormString(String answer){
        if (answer == null || answer.equals(""))
            return new ArrayList();

        JSONArray jsonArray = JSONArray.fromObject(answer);
        List list = (List) JSONArray.toCollection(jsonArray,
                Answer.class);

        return list;
    }

    /**
     *
     * 将一个 Answer 对象的List 生成Json字串
     * 是根据客户端页面用户输入的信息生成的
     *
     *
     */
    public String getAnswerString(String[] studenAnswers, int[] question_ids,
            int[] types,int[] scores) {
        List list = toAnswerList(studenAnswers,  question_ids,
                 types, scores);
        JSONArray jsonarray = JSONArray.fromObject(list);

        return jsonarray.toString();
    }