2. Add Two Numbers LeetCode Java

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

Solution:
My solution is straightforward, as long as l1,l2 is not null or carry is non-zero, create a new ListNode by calculating the sum and updating the carry. This method require some attention of processing null-pointer. l1 and l2 are both possibly null when they are iterated. 

 public ListNode addTwoNumbers(ListNode l1, ListNode l2) {  
    if(l1==null && l2==null) return null;  
    ListNode predummy=new ListNode(0);  
    ListNode pre=predummy;  
    ListNode cur1=l1;  
    ListNode cur2=l2;  
    int sum=0;  
    int carry=0;  
    while(cur1!=null || cur2!=null || carry!=0){  
      int num1=(cur1==null)? 0: cur1.val;  
      int num2=(cur2==null)? 0: cur2.val;  
      sum=num1+num2+carry;  
      ListNode temp=new ListNode(sum%10);  
      pre.next=temp;  
      pre=pre.next;  
      carry=sum/10;  
      if(cur1!=null) cur1=cur1.next;  
      if(cur2!=null) cur2=cur2.next;  
    }  
    return predummy.next;  
   }