Leetcode 82 Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

Solution 1:  Use dummy node for deleting.

 public class Solution {  
   public ListNode deleteDuplicates(ListNode head) {  
     ListNode dummy=new ListNode(0);  
     dummy.next=head;  
     ListNode i=dummy;  
     while (i.next!=null && i.next.next!=null) {  
       if (i.next.val!=i.next.next.val) i=i.next;  
       else {  
         ListNode j=i.next;  
         while (j.next!=null && j.val==j.next.val) j=j.next;  
         i.next=j.next;  
       }  
     }  
     return dummy.next;  
   }  
 }