Palindrome Number

Check if an integer is a palindrome number without extra space cost (cost $O(1)$ as we at least need another variable). So it is not allowed to turn the number into String with String.valueOf(x). This problem is in fact quite simple but one should take care of the cases that may cause one or more variable's value exceed their type's limit.

public class PalindromeNumber {
    public static boolean isPalindrome(int x) {
        if (x < 0) return false;

        long l = 1; // must use long here
        long r = 10;
        while (x / l >= 10) l *= 10;

        while (l >= r) {
            long left = (x % (l * 10)) / l;
            long right = (x % r) * 10 / r;
            if (left != right) return false;

            l /= 10;
            r *= 10;
        }

        return true;
    }
}