替我找错误

正确的我就不说了。
为啥下面的解法不对？

/*
 public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}
*/
import java.util.*;
public class Solution {

    //方案2:双指针
    public ListNode EntryNodeOfLoop(ListNode pHead)
    {
        if(pHead==null||pHead.next==null||pHead.next.next==null) return null;

        ListNode fast = pHead.next.next;
        ListNode slow = pHead;
        while(true){
            if(fast==slow){
                fast = pHead;
                break;
            }
            if(fast.next==null||fast.next.next==null){
                return null;
            }
            fast = fast.next.next;
            slow = slow.next;
        }

        while(fast!=slow){
            fast = fast.next;
            slow = slow.next;
        }
        return fast;



    }
}