package com.ecust.jvm5;
import java.util.Stack;
/**
* 用两个栈来实现一个队列
* @author liuxin
*
* @param <E>
*/
public class QueueWithTwoStacks<E> {
private Stack<E> stack1;
private Stack<E> stack2;
public QueueWithTwoStacks() {
stack1 = new Stack<E>();
stack2 = new Stack<E>();
}
public boolean isEmpty() {
return stack1.isEmpty();
}
public int size() {
return stack1.size();
}
public void enQueue(E item) {
stack1.push(item);
}
public E deQueue() {
if (stack1.isEmpty()) {
return null;
}
while (!stack1.isEmpty()) {
stack2.push(stack1.pop());
}
E e = stack2.pop();
while (!stack2.isEmpty()) {
stack1.push(stack2.pop());
}
return e;
}
public static void main(String[] args) {
QueueWithTwoStacks queue = new QueueWithTwoStacks();
queue.enQueue(1);
queue.enQueue(2);
queue.enQueue(3);
queue.enQueue(4);
queue.enQueue(5);
queue.enQueue(6);
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());System.out.println(queue.deQueue());System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
queue.enQueue(7);
queue.enQueue(8);
queue.enQueue(9);
queue.enQueue(0);
queue.enQueue(1);
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
System.out.println(queue.deQueue());
}
}