/** * Created by lifei on 16/6/28. * * 从两头依次取数字比较，向中间推进。 */public class IsPalindrome {    public static void main(String[] args) {        IsPalindrome ip = new IsPalindrome();        System.out.println(ip.isPalindrome(1221));    }    public boolean isPalindrome(int x) {        if (x < 0)            return false;        //calcu the length of digit        int len = 1;        while (x / len >= 10) {   //得到最大的除数            len *= 10;        }        while (x != 0) {            int left = x / len;            int right = x % 10;            if (left != right)                return false;            //remove the head and tail digit            x = (x % len) / 10;    //把余数作为下一次遍历对象   x%len去掉高位,  再 /10去低位            len /= 100;            //减少len的步长        }        return true;    }}