末尾0的个数

/** * Created by lihaibin02 on 2016/9/18. */ public class Test {    public static int count_Number(int n) {        int sum = 0;        for(int i=1;i<=n;i++){//可以再优化   for(int i=5;i<=n;i+=5)         int j=i;            while (j%5==0)            {                sum++;                j/=5;            }        }        return sum;    }    public static void main(String[] args) {        System.out.println(count_Number(1000));    }}-------------答案：249