java 拆分数字

public class MyInteger {
　　// System.out.println(NumberAt(998156452, 4)); //返回 6

　　public static int NumberAt(Integer num, int unit) {
        if (unit == 1) return num % 10;
        int after = 1;
        while (--unit > 0) after *= 10;
        int rest = num % after;
        return ((num - rest) / after) % 10;
    }

    public static int NumberLength(Integer num) {
        int len = 1, sum = 10;
        while (num >= sum) {
            sum *= 10;
            len++;
        }
        return len;
    }
}