只用于记载工作学习到的知识

1.随机日期

 /**
     * 获取随机日期
     * @param beginDate 起始日期
     * @param endDate 结束日期
     * @return
     */
    public static Date randomDate(String beginDate,String endDate){
        try {
            SimpleDateFormat format = new SimpleDateFormat(DateUtil.STANDARD_DATETIME_PATTERN);
            Date start = format.parse(beginDate);
            Date end = format.parse(endDate);

            if(start.getTime() >= end.getTime()){
                return null;
            }

            long date = random(start.getTime(),end.getTime());

            return new Date(date);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    private static long random(long begin,long end){
        long rtn = begin + (long)(Math.random() * (end - begin));
        if(rtn == begin || rtn == end){
            return random(begin,end);
        }
        return rtn;
    }

2.mysql 随机查询数据 

SELECT * FROM tb_paddling_name as t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(id) FROM tb_paddling_name)) as id) as t2 WHERE t1.id >= t2.id ORDER BY t1.id asc LIMIT 1;

3.int 值 两数之间随机案例

  //年龄区间  强制转换总是向下取值 所以 最大+1 - 最小值 被 1以下随机数相乘 + 最小数
 Integer age = (int) Math.random() * (userDto.getAgeBig() + 1 - userDto.getAgeSmall()) + userDto.getAgeSmall();