Remove Nth Node From End of List

https://leetcode.com/problems/remove-nth-node-from-end-of-list/

Given a linked list, remove the nth 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.

public class Solution {
    public static ListNode removeNthFromEnd(ListNode head, int n) {
    ListNode li=head;
        int len=0;
        while(li!=null){
            len++;
            li=li.next;
        }
        int index=len-n+1;
        if(index==1){return head.next;}
        li=head;
        ListNode pre_li=li;
        while(index-->1){
            pre_li=li;
            li=li.next;
        }
        pre_li.next=li.next;
        return head;
    }
//    public static class ListNode {
//    int val;
//    ListNode next;
//
//    ListNode(int x) {
//        val = x;
//    }
//    }
    public static void main(String[]args){
    ListNode[]node=new ListNode[4];
    for(int i=0;i<node.length;i++){
        node[i]=new ListNode(i);
    }
    node[0].next=node[1];
    node[1].next=node[2];
    node[2].next=node[3];
    ListNode head=removeNthFromEnd(node[0],2);
    while(head!=null){
        System.out.println(head.val);
        head=head.next;
    }
    }
}