考虑唯一字符串，取出17位当前时间戳  + 3位随机数字

 

//获取当前时间戳
    public static String getTimeStr(){
        StringBuffer sb = new StringBuffer();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS");
        sb.append(sdf.format(new Date())).append((int) (Math.random() * 900) + 100);
        return sb.toString();//20190319222821840453
    }