package zy813ture;

public class MyArrayQueue1 {//双向循环数组

	private Object []obj;

	private int front;

	private int last;

	//private int MAXQSIZE;

	public MyArrayQueue1() {

		obj = new Object[4];

	}

	public boolean offer(Object element) {// 将指定的元素插入此队列

		if(element==null)

			 throw new NullPointerException ("元素为null");

		if(last==front && obj[front] !=null){    //判断此队列是否队满

			return false;

		}

		obj[last] = element;

		last = (last + 1) % obj.length;

		return true;

	}

	public Object peek(){// 获取不移除此队列的头；如果此队列为空，则返回 null

		if(last == front && obj[front] == null)   //判断此队列是否为空

			return null;

		return obj[front];

	}

	public Object poll(){// 获取并移除此队列的头；如果此队列为空，则返回 null

		if(last == front && obj[front] == null)   //判断此队列是否为空

			return null;

		Object o = obj[front];//定义个o放置第一个

		obj[front]=null;//移除

		front=(front+1)%obj.length;//移除第一个后front变成front+1；

		return o;

		}

	public static void main(String[] args) {

		MyArrayQueue1 me= new MyArrayQueue1();

	    me.offer("ab1");

		me.offer("ab2");

		me.offer("ab3");

		//System.out.println(me.peek());// ab1 空的话为null

		//System.out.println(me.poll());// ab1 空的话为null

		//System.out.println(me.peek());// ab2 空的话为null

		System.out.println(me.peek());// ab2 空的话为null

	}

}