leetcode--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.

/**
 * 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){
			ListNode currentFirst = head;
			ListNode currentNode = head.next;
			while(currentNode != null){
				if(currentFirst.val != currentNode.val){
					currentFirst.next = currentNode;
					currentFirst = currentFirst.next;
				}
				currentNode = currentNode.next;
			}
			if(currentFirst.next != null)
			    currentFirst.next = null;
		}
		return head;    
    }
}