public static void main(String[] args) throws Exception{    {        //Math函数的四舍五入，注意负数的时候小数位<=0.5都会被舍去,>0.5的才会被进位        System.out.println(Math.round(15.5));        System.out.println(Math.round(-15.5));        System.out.println(Math.round(-15.51));    }    {        //用Random类生成随机数        List<Integer> intList = new ArrayList<Integer>();        Random random = new Random();        int count = 0;        while(count <= 7)        {            Integer tem = random.nextInt(37);            if(intList.contains(tem))                continue;            else            {                intList.add(tem);                count++;             }        }                System.out.println(intList);    }    {        //大整数的加减乘除        BigInteger bigA = new BigInteger("132122332323232323");        BigInteger bigB = new BigInteger("45648945649874645645645641231974816");        System.out.println(bigA);        System.out.println(bigB);        System.out.println(bigA.multiply(bigB));    }    {        //大小数的四舍五入        BigDecimal bd = new BigDecimal("12358645.22564");        System.out.println(bd.divide(new BigDecimal("1"), 1, BigDecimal.ROUND_HALF_UP));;    }}