Generate a specified length verification code in Java

Generate a specified length verification code in Java

1. Method 1: high execution efficiency

  /**
     * 生成指定位数验证码,纯数字运算效率最高
     *
     * @param maxSize
     * @return
     */
    public static Long generateRandomCode(int maxSize) {
        if (maxSize < 0) {
            throw new BizException(ErrorCodeEnum.PARAM_ERROR);
        }
        //小数点后16位的double乘以10的指定次幂然后取整
        String code = String.valueOf((int) ((Math.random() * 9 + 1) * Math.pow(10, maxSize - 1)));
        Long resultCode = Long.valueOf(code);
        return resultCode;
    }
   

2. Method 2: String interception

    /**
     * 生成指定位数验证码,字符串截取,效率不如方法一
     *
     * @param maxSize
     * @return
     */
    public static Long generateSubStringCode(int maxSize) {
        if (maxSize < 0) {
            throw new BizException(ErrorCodeEnum.PARAM_ERROR);
        }
        //16位double小数,取小数点后的2-8位
        int startNum = 2;
        int endNum = startNum + maxSize;
        String code = (Math.random() + "").substring(startNum, endNum);
        Long resultCode = Long.valueOf(code);
        return resultCode;
    }