Remove Nth Node From End of List

Given the head of a linked list, remove the nth node from the end of the list and return its head.

Follow up: Could you do this in one pass? 

Example 1:

Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]

Example 2:

Input: head = [1], n = 1
Output: []

Example 3:

Input: head = [1,2], n = 1
Output: [1]

Solution:

public ListNode removeNthFromEnd(ListNode head, int n) {
        if(head == null)
            return head;        
        ListNode dummy = new ListNode(0);
        dummy.next = head;        
        ListNode first, second;
        first=second=dummy;
        for(int i=0; i<n+1; i++) {
            first=first.next;
        }
        while(first!=null){
            first=first.next;
            second=second.next;
        }
        // Remove nth node from end
        second.next = second.next.next;
        return dummy.next;
    }