《剑指Offer》题目——从尾到头打印链表

public class ReverseList {
    class ListNode{
        int val;
        ListNode next = null;

        ListNode(int val){
            this.val = val;
        }
    }
    public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
        Stack<Integer> stack = new Stack<Integer>();
        ArrayList<Integer> list = new ArrayList<Integer>();

        //注意这里while循环结束的条件是listNode不为空，而不是listNode.next不为空
        while (listNode!=null){
            stack.push(listNode.val);
            listNode = listNode.next;
        }
        while (!stack.empty()){
            list.add(stack.pop());
        }
        return list;
    }
    public static void main(String[] args){

    }
}