环形队列-数组简单实现_环形队列数组-优快云博客

本文链接：https://blog.youkuaiyun.com/chenkui199/article/details/123949600

该博客介绍了Java中循环队列的实现，包括初始化、入队、出队、容量检查和动态扩容功能。示例代码展示了如何在队列满时扩容至原容量的两倍，以及在队列元素数量低于容量的25%时缩容至原容量的一半。通过调用`enQueue`和`deQueue`方法展示了队列操作。

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package demo;

/**
 * ѭ������
 * 
 * @author Administrator
 *
 */
public class LoopQueue<E> {

	private E[] data;
	private int front, tail;
	private int size;
	private final static int growFactor = 2;
	private final static double compressThreadhold = 0.25;

	public LoopQueue() {
		this(10);
	}

	public LoopQueue(int capacity) {
		if (capacity <= 0)
			throw new IllegalArgumentException("��������С��0");
		data = (E[]) new Object[capacity + 1];
		front = 0;
		tail = 0;
		size = 0;
	}

	public int getCapacity() {
		return data.length - 1;
	}

	public int getSize() {
		return size;
	}

	public boolean isEmpty() {
		return front == tail;
	}

	public boolean isFull() {
		return (tail + 1) % data.length == front;
	}

	public void enQueue(E e) throws IllegalAccessException {
		if (e == null)
			throw new IllegalArgumentException("��������Ϊ��");
		if (isFull())
			resize(data.length * growFactor);
		data[tail] = e;
		tail = (tail + 1) % data.length;
		size++;
	}

	public E deQueue() {
		E result = null;
		if (isEmpty())
			throw new IllegalAccessError("����Ϊ��");
		result = data[front];
		front = (front + 1) % data.length;
		size--;
		if (size < (data.length * compressThreadhold))
			resize(data.length / growFactor);
		return result;
	}

	private void resize(int capacity) {
		E[] ndata = (E[]) new Object[capacity + 1];
		for (int i = 0; i < size; i++) {
			ndata[i] = data[(i + front) % data.length];
		}
		System.out.println("����һ��....");
		data = ndata;
		front = 0;
		tail = size;
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append("queue [");
		for (int i = front; i != tail; i = (i + 1) % data.length) {
			sb.append(data[i]);
			sb.append(" ,");
		}
		sb.append("] tail");
		return sb.toString();
	}

	public static void main(String[] args) throws Exception {
		LoopQueue<Integer> lq = new LoopQueue<Integer>();
		for (int i = 0; i < 50; i++) {
			lq.enQueue(i);
		}
		System.out.println(lq);
		System.out.println(lq.getCapacity() + ":" + lq.getSize());
		System.out.println("==================================");
		for (int i = 0; i < 40; i++) {
			lq.deQueue();
		}
		System.out.println(lq);
		System.out.println(lq.getCapacity() + ":" + lq.getSize());
	}

}