import java.util.Stack;
public class Solution {
public ListNode ReverseList(ListNode head) {
    Stack<ListNode> stack= new Stack<>();
    //把鏈表節(jié)點全部摘掉放到棧中
    while (head != null) {
        stack.push(head);
        head = head.next;
    }
    if (stack.isEmpty())
        return null;
    ListNode node = stack.pop();
    ListNode dummy = node;
    //棧中的結點全部出棧，然后重新連成一個新的鏈表
    while (!stack.isEmpty()) {
        ListNode tempNode = stack.pop();
        node.next = tempNode;
        node = node.next;
    }
    //最后一個結點就是反轉前的頭結點，一定要讓他的next
    //等于空，否則會構成環(huán)
    node.next = null;
    return dummy;
}
}

加油沖