java相关-用栈实现队列-力扣232

package com.company;

import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Stack;

public class MyQueue {
    private Stack<Integer> stackIn;
    private Stack<Integer> stackOut;


    public MyQueue() {
        stackIn = new Stack<>();
        stackOut = new Stack<>();
    }


    public void push(int x) {
        stackIn.push(x);//这里必须是装到stackIn里面，因为后续dumpstackIn倒入元素是从stackIn倒入到stackOut
    }

    //弹出顶端值
    public int pop() {
        dumpstackIn();
        return stackOut.pop();
    }

    //获取顶端值，不弹出
    public int peek() {
        dumpstackIn();
        return stackOut.peek();
    }

    public boolean empty() {
        return stackIn.isEmpty() && stackOut.isEmpty();

    }

    private void dumpstackIn() {//如果stackOut为空，那么将stackIn中的元素全部放到stackOut中
        if (!stackOut.isEmpty()) {
            return;
        }
        while (!stackIn.isEmpty()) {
            stackOut.push(stackIn.pop());//弹出stackIn中的元素放到stackOut里
        }
    }
}

package com.company;


import java.util.*;

public class Main {

    public static void main(String[] args) {

        MyQueue queue=new MyQueue();


        queue.push(1);
        queue.push(2);
        queue.push(3);
        System.out.println(queue.pop());
        System.out.println(queue.pop());
        System.out.println(queue.peek());

    }





}