Java 随机数&字符串

一、随机小数
Math.random()；

二、指定范围内的随机数
大于等于0，小于1000
RandomUtils.nextInt(0, 1000)

三、返回指定范围内的随机时间
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(testcaseTools.randomDate("2019-01-01","2019-12-31"))

    public Date randomDate(String beginDate,String endDate) {
        try {
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
            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;
    }

    public 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;
    }

四、返回指定长度的字符串
chars 定义字符串的取值范围（字母区分大小写）

    public String generateRandomAllLowercaseLettersAndNumberString(int length) {
        String chars = "abcdefghijklmnopqrstuvwxyz0123456789";
        StringBuilder sb = new StringBuilder();
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            int index = random.nextInt(chars.length());
            sb.append(chars.charAt(index));
        }
        return sb.toString();
    }