/**
     * 生成訂單編號  時間戳+3位整數
     * @return
     */
    public String autoOrderId(){

        Date date = new Date();
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String str = format.format(date);
        Date orderId = null;
        Random rand = new Random();
        //[900]：900個    100：從100
        int x = rand.nextInt(900) + 100;
        try {
           orderId = format.parse(str);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return String.valueOf(orderId.getTime()) + x;
    }