数据结构之java实现队列(二)

来源：互联网发布：linux vi e325 编辑：程序博客网时间：2024/04/29 15:51

这一篇文章是上一篇文章的改进实现

使用计数器代替尾指针来使队列真正容量达到maxSize

队头指针：front

计数器: count;

队空条件：count == 0

队满条件：count == maxSize

进队操作：count++，(front+count)%masSize

出队操作：count--，front = (front+1)%maxSize

利用了计数器count，可以将队列的最大容量为maxSize，而不用空出一个单元

public class Queue<E> {E[] queue;int front;int count;int maxSize;private final static int DEFAULT_SIZE = 10;public Queue() throws Exception{this(DEFAULT_SIZE);}public Queue(int capacity) throws Exception{if(capacity < 0)throw new Exception("Illegal capacity ");queue = (E[]) new Object[capacity];front = 0;count = 0;maxSize = capacity;}//--------元素进入队列算法----------public boolean enQueue(E obj) throws Exception{if(obj == null)return false;//判断是否队满if(count == maxSize)throw new Exception("Queue is full ");//进队操作count++;queue[(front + count) % maxSize] = obj;return true;}//------------元素出队算法---------------public E deQueue() throws Exception{//判断队空if(count == 0)throw new Exception("Queue is empty");//出队操作count--;front = (front+1) % maxSize;return queue[front];}//-------------判断队空算法--------------public boolean isEmpty(){return (count == 0) ? true:false;}//------------求队列元素个数算法-------------public int countElem(){return count;}    //-------------输出队列算法----------------public void display() throws Exception{if(count == 0)throw new Exception("Queue is empty ");int index = (front+1)%maxSize;int n = count;while(n != 0){System.out.println(queue[index]);index = (index+1)%maxSize;n--;}}public static void main(String[] args) throws Exception{Queue queue = new Queue(100);for(int i=1;i<=100;i++)queue.enQueue(i);System.out.println("队列元素个数：" + queue.countElem());System.out.println("队列是否为空：" + queue.isEmpty());System.out.println("**********************************");for(int i=1;i<=50;i++)queue.deQueue();System.out.println("队列元素个数：" + queue.countElem());System.out.println("队列是否为空：" + queue.isEmpty());System.out.println("**********************************");for(int i=1;i<=50;i++)queue.deQueue();System.out.println("队列元素个数：" + queue.countElem());System.out.println("队列是否为空：" + queue.isEmpty());}}

0 0