leetcode Swap Nodes in Pairs

 1 public class Solution {
 2   public ListNode swapPairs(ListNode head) {
 3     ListNode start = new ListNode(0); //make head no longer a special case
 4     start.next = head;
 5 
 6     for(ListNode cur = start; cur.next != null && cur.next.next != null; cur = cur.next.next) {
 7       cur.next = swap(cur.next, cur.next.next);        
 8     }
 9     return start.next;
10   }
11   private Listnode swap(ListNode next1, ListNode next2) {
12     next1.next = next2.next;
13     next2.next = next1;
14     return next2;
15   }
16 }