队列的理解和实现(二) ----- 链队列(java实现)

什么是链队列

链队是指采用链式存储结构实现的队列，通常链队用单链表俩表示。一个链队显然需要两个分别指示队头和队尾的指针，也称为头指针和尾指针，有了这两个指针才能唯一的确定。

package 链队列;

public class LinkQueue {

	class Element {
		Object data;
		Element next;
		public Element() {
			this.data = null;
			this.next = null;
		}

		public Element(Object data) {
			this.data = data;
			this.next = null;
		}

		public Element(Object data, Element next) {
			this.data = data;
			this.next = next;
		}
	}

	private Element front;
	private Element rear;

	public LinkQueue() {
		front = null;
		rear = null;
	}

	public void enQueue(Object data) {
		Element e = new Element(data);
		if(this.front != null) {
			this.rear.next = e;
			rear = e;
		}
		else {
			this.front = this.rear = e;
		}
	}

	public void deQueue() {
		if(this.front != null) {
			Element p = front;
			front = front.next;
			if(p == rear) { //队列中只有一个元素
				rear = null;
			}
		}
		else System.out.println("队列为空");
	}

	public Object getHead() {
		if(front != null) {
			return front.data;
		}
		else return null;
	}

	public int getLength() {
		Element p = front;
		int length = 0;
		while(p != null) {
			p = p.next;
			length++;
		}
		return length;
	}

	public boolean isEmpty() {
		return front == null ? true : false;
	}

	public static void main(String[] args) {
		LinkQueue q = new LinkQueue();
		System.out.println("队列是否为空：" + q.isEmpty());
		System.out.println("连续入队＝＝＝＝＝＝＝＝＝");
		for (int i = 0; i < 5; i++) {
			q.enQueue(i);
		}
		System.out.println("队列的长度为: " + q.getLength());
		System.out.println("队首元素为:" + q.getHead());

		System.out.println("连续出队＝＝＝＝＝＝＝＝＝");
		for (int i = 0; i < 3; i++) {
			q.deQueue();
		}

		System.out.println("队列是否为空：" + q.isEmpty());
		System.out.println("队列的长度为: " + q.getLength());
		System.out.println("队首元素为:" + q.getHead());

	}
}