public static void main(String[] args) {
    AddTwoNumbers test = new AddTwoNumbers();

    ListNode l1 = test.new ListNode(5);
    ListNode l2 = test.new ListNode(5);

    test.addTwoNumbers(l1, l2);
  }
 public static void main(String[] args) {
   int arr1[] = {2, 4, 3};
   int arr2[] = {5, 6, 7};
   ListNode a = createListFromArray(arr1);
   ListNode b = createListFromArray(arr2);
   AddTwoNumbers atn = new AddTwoNumbers();
   ListNode sum = atn.addTwoNumbers(a, b);
   showList(sum);
 }