LeetCode2.java

 // Definition for singly-linked list.
  public class ListNode {
      int val;
      ListNode next;
      ListNode() {}
      ListNode(int val) { this.val = val; }
      ListNode(int val, ListNode next) { this.val = val; this.next = next; }
  }
 
class LeetCode2 {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
       ListNode result = new ListNode(0);
       ListNode ptr = result;

       int carry = 0;

       while (l1!=null || l2!=null){
           int sum = 0+carry;

           if (l1!=null){
               sum+=l1.val;
               l1=l1.next;
           }
          if (l2!=null){
               sum+=l2.val;
               l2=l2.next;
           } 

           carry = sum/10;
           sum = sum % 10;
           ptr.next = new ListNode(sum);
           ptr = ptr.next;
       }
       if (carry==1) ptr.next = new ListNode(1);
           return result.next;
    }

}
//LeetCode 2. Add Two Numbers
//Case l1 = [2,4,3] | l2 = [5,6,2]