Remove duplicates from sorted list

Given a sorted linked list, delete all duplicates such that each element appear only once.

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

Easy one, if you are not too inexperienced with linkedlist

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */public class Solution {    public ListNode deleteDuplicates(ListNode head) {        if(head == null) {            return null;        }        if (head.next == null){            return head;        }                ListNode previous = head;        while(previous!=null){            ListNode next = previous.next;            if(next!=null && next.val == previous.val){                next = next.next;                previous.next = next;            }            else{                previous = previous.next;                           }        }        return head;    }}