LeetCode 83 - 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.

public ListNode deleteDuplicates(ListNode head) {
    ListNode p = head;
    while(p != null && p.next != null) {
        if(p.next.val == p.val){
            p.next = p.next.next;
        } else {
            p = p.next;
        }
    }
    return head;
}