private Node addRemaining(Node start, Node stop){
        if(start != stop){
            Node result = Node.newNode(0);
            result.next = addRemaining(start.next , stop);
            result.data = (start.data + carry)%10;
            carry = (start.data + carry)/10;
            return result;
        }else{
            return null;
        }
    }
http://www.geeksforgeeks.org/sum-of-two-linked-lists/
Test case
Either of list is null
Size of list1 is greater, equal or smaller than list2
Add with carry in main
Add with carry in remaining
src/com/interview/linklist/AddNumberRepresentedByLinkList.java