环形队列-数组简单实现

package demo;

/**
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 * 
 * @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("����������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("����������");
        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("������");
        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());
    }

}