LeetCode - Remove Nth Node From End of List

Given a linked list, remove the n^th node from the end of list and return its head.
For example,

   Given linked list: 1->2->3->4->5, and n = 2.

   After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:
Given n will always be valid.
Try to do this in one pass.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        if(head==null) {
            return null;
        }
        ListNode p1 = head;
        ListNode p2 = head;
        int m = n;
        while(m-->0) {
            p2 = p2.next;
        }
        if(p2==null) {
            return head.next;
        }
        while(p2.next!=null) {
            p1 = p1.next;
            p2 = p2.next;
        }
        p1.next = p1.next.next;
        return head;
    }
}