package com.sxt.test.java;public class Stack2Queue {/*** 用栈的入栈和出栈* 来实现队列的入队和出队*  stack1是入栈的，stack2是出栈的。入队列：直接压入stack1即可出队列：如果stack2不为空，把stack2中的栈顶元素直接弹出；否则，把stack1的所有元素全部弹出压入stack2中，再弹出stack2的栈顶元素* */Stack stack1 = new Stack();Stack stack2 = new Stack();public void add(Object o) {stack1.push(o);}public Object poll() {Object o = null;if(stack2.length()==0) {//把stack1的数据放入stack2，留下最后一个数据while(stack1.length()>1) {stack2.push(stack1.pop());}if(stack1.length()==1) {//把stack1的留下的那个数据返回出去o = stack1.pop();}}else {o = stack2.pop();}return o;}public int length() {return stack1.length()+stack2.length();}}

package com.sxt.test.java;public class Queue2Stack {/*** 用队列的入队和出队* 来实现栈的入栈和出栈* */Queue queue1 = new Queue();//主要存放数据Queue queue2 = new Queue();//辅助public void push(Object o) {queue1.add(o);}public Object pop() {Object o = null;while(queue1.length()>1) {queue2.add(queue1.poll());}if(queue1.length()==1) {o = queue1.poll();while(queue2.length()>0) {queue1.add(queue2.poll());}}return o;}public int length() {return queue1.length();}}

/*** 用两个栈实现队列* */Stack2Queue stack2Queue = new Stack2Queue();stack2Queue.add("a");stack2Queue.add("b");stack2Queue.add("c");stack2Queue.add("d");stack2Queue.add("e");while(stack2Queue.length()>0) {System.out.println(stack2Queue.poll());}/*** 用两个队列实现栈* */Queue2Stack queue2Stack = new Queue2Stack();queue2Stack.push("a");queue2Stack.push("c");queue2Stack.pop();queue2Stack.push("d");queue2Stack.push("e");queue2Stack.push("f");queue2Stack.push("g");queue2Stack.push("h");while(queue2Stack.length()>0) {System.out.println(queue2Stack.pop());}