单线程无锁读写缓存

来源：互联网发布：淘宝上冰毒暗语编辑：程序博客网时间：2024/06/06 16:59
import java.util.Arrays;/** * 创建一个循环队列（环形缓冲、RingBuffer），实际元素存在一个数组中，操作数组的指针，不移动元素 * <p/> * 需要说明是：支持单线程无锁读与写 */public class CircleQueue<T>{    //      循环队列 （数组）默认大小    private final int DEFAULT_SIZE = 1000;    //      (循环队列)数组的容量    public int capacity;    //      数组：保存循环队列的元素    public Object[] elementData;    //      队头(先见先出)    public int head = 0;    //      队尾    public int tail = 0;    //      以循环队列 默认大小创建空循环队列    public CircleQueue()    {        capacity = DEFAULT_SIZE;        elementData = new Object[capacity];    }    public CircleQueue(final int initSize)    {        capacity = initSize;        elementData = new Object[capacity];    }    /**     * 获取循环队列的大小(包含元素的个数)     */    public int size()    {        if (isEmpty())        {            return 0;        } else if (isFull())        {            return capacity;        } else        {            return tail + 1;        }    }    /**     * 插入队尾一个元素     */    public void add(final T element)    {        if (isEmpty())        {            elementData[0] = element;        } else if (isFull())        {            elementData[head] = element;            head++;            tail++;            head = head == capacity ? 0 : head;            tail = tail == capacity ? 0 : tail;        } else        {            elementData[tail + 1] = element;            tail++;        }    }    public boolean isEmpty()    {        return tail == head && tail == 0 && elementData[tail] == null;    }    public boolean isFull()    {        return head != 0 && head - tail == 1 || head == 0 && tail == capacity - 1;    }    public void clear()    {        Arrays.fill(elementData, null);        head = 0;        tail = 0;    }    /**     * @return 取 循环队列里的值（先进的index=0）     */    public Object[] getQueue()    {        final Object[] elementDataSort = new Object[capacity];        final Object[] elementDataCopy = elementData.clone();        if (isEmpty())        {        } else if (isFull())        {            int indexMax = capacity;            int indexSort = 0;            for (int i = head; i < indexMax; )            {                elementDataSort[indexSort] = elementDataCopy[i];                indexSort++;                i++;                if (i == capacity)                {                    i = 0;                    indexMax = head;                }            }        } else        {            // elementDataSort = elementDataCopy;//用这行代码代替下面的循环，在队列刚满时候会出错            for (int i = 0; i < tail; i++)            {                elementDataSort[i] = elementDataCopy[i];            }        }        return elementDataSort;    } }
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