熟悉栈和队列的方法；熟悉栈和队列的数据结构，不涉及算法

232.用栈实现队列

import java.util.Stack;
class MyQueue {//负责进栈的Stack<Integer> stackIn;//负责出栈的Stack<Integer> stackOut;public MyQueue() {stackIn = new Stack<>();stackOut = new Stack<>();}public void push(int x) {stackIn.push(x);}public int pop() {if(stackOut.isEmpty()) dumpsStackIn();return stackOut.pop();}public int peek() {if(stackOut.isEmpty()) dumpsStackIn();return stackOut.peek();}public boolean empty() {return stackOut.isEmpty()&& stackIn.isEmpty();}public void dumpsStackIn(){while(!stackIn.isEmpty()) stackOut.push(stackIn.pop());}
}

225. 用队列实现栈

class MyStack {Queue<Integer> q1;Queue<Integer> q2;public MyStack() {q1 = new LinkedList();q2 = new LinkedList();}public void push(int x) {q2.offer(x);while(!q1.isEmpty()) q2.offer(q1.poll());Queue tmpQueue = q2;q2 = q1;q1 = tmpQueue;}public int pop() {return q1.poll();}public int top() {return q1.peek();}public boolean empty() {return q1.isEmpty();}
}