leetcode 2. Add Two Numbers

It's really tired after a whole day's work and a phone interview after work.
So I decided to relax and end today with a nice and easy and two numbers.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int rest = 0;
        ListNode head = new ListNode(0);
        ListNode ptr = head;
        while (l1 != null || l2 != null) {
            int val = rest;
            if (l1 != null) {
                val += l1.val;
                l1 = l1.next;
            }
            if (l2 != null) {
                val += l2.val;
                l2 = l2.next;
            }
            ptr.next = new ListNode(val % 10);
            rest = val / 10;
            ptr = ptr.next;
        }
        if (rest != 0) ptr.next = new ListNode(rest);
        return head.next;
    }

}