模拟一个队列(java)

简介
队列是一种特殊的线性表，它只允许在表的前端（front）进行删除操作，而在表的后端（rear）进行插入操作。进行插入操作的端称为队尾，进行删除操作的端称为队头。队列中没有元素时，称为空队列。
在队列这种数据结构中，最先插入的元素将是最先被删除的元素；反之最后插入的元素将最后被删除的元素，因此队列又称为“先进先出”（FIFO—first in first out）的线性表。 　　
队列空的条件： front=rear 　　
队列满的条件： rear = MAXSIZE

/**
 * simulate queue struct by java
 * 
 * @author Bruce
 * @date Sep 8, 2011
 * @version 1.0
 */

public class Queue {
	private int maxSize;
	private long[] queueArray;
	private int front;// the head of queue
	private int rear;// the end of queue
	private int nItems;

	/**
	 * Constructor a queue,the size is s;now the queue is null, and the front is
	 * zero and the rear is negative one
	 * 
	 * @param s
	 */
	public Queue(int s) {
		maxSize = s;
		queueArray = new long[maxSize];
		front = 0;
		rear = 0;
		nItems = 0;
	}

	public void insert(long j) {
		// if the the inserted items great the size of queue,
		// the rear return the initial value and the next item will
		// override the corresponding value
		if (rear == maxSize)
			rear = 0;
		queueArray[rear++] = j;
		nItems++;// the count of the items
	}

	/**
	 * remove the item from the 'front' position,every time the front will be
	 * added one
	 */
	public long remove() {
		long temp = queueArray[front++];
		// if the front equals the size of queue,the front will return the
		// initial value
		if (front == maxSize)
			front = 0;
		nItems--;
		if (nItems < 0)
			nItems = 0;
		return temp;
	}

	public long peekFront() {
		return queueArray[front];
	}

	public boolean isEmpty() {
		return (nItems == 0);
	}

	public boolean isFull() {
		return (nItems == maxSize);
	}

	public int size() {
		return nItems;
	}

	public static void main(String[] args) {
		Queue queue = new Queue(3);
		queue.insert(3);
		queue.insert(6);
		queue.insert(8);
		// queue.insert(4);

		System.out.println("size:" + queue.size());

		System.out.println(queue.peekFront());
		queue.remove();
		System.out.println(queue.peekFront());
		queue.remove();
		System.out.println(queue.peekFront());
		queue.remove();
		// System.out.println(queue.peekFront());
		// queue.remove();

		System.out.println("size:" + queue.size());

	}

}