题解 | #两个队列实现栈#

import java.util.*;

public class Solution {
    Queue<Integer> queue1 = new LinkedList();
    Queue<Integer> queue2 = new LinkedList();
    
    public void push(int element) {
        while (!queue1.isEmpty()) {
            queue2.add(queue1.poll());
        }
        queue1.add(element);
        while (!queue2.isEmpty()) {
            queue1.add(queue2.poll());
        }
    }
    
    public int pop() {
        return queue1.poll();
    }
    
    public int top() {
        return queue1.peek();
    }
    
    public boolean empty() {
        return queue1.isEmpty();
    }
}