java 使用ReentrantLock Condition实现阻塞队列

package test;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** * 阻塞队列简单实现。 * 先进先出 * * @author ZRD * @since 2016-3-23 上午10:05:37 * @ClassName BlockingQueue */public class BlockingQueue {private Object[] data;//数据对象private int count = 0;//当前数据对象中含有多少个数据private int addPosition = 0;//当前add数据的索引位置private int takePosition = 0;//当前take数据的索引位置private Lock lock = new ReentrantLock();// 线程锁private Condition addCondition = lock.newCondition();// 添加条件private Condition takeCondition = lock.newCondition();// 取出条件public BlockingQueue(int size) {data = new Object[size];}public void add(Object value) {lock.lock();// 线程加锁try {while (count == data.length) {// 队列已经满了try {//System.out.println("add await thread:" + Thread.currentThread().getName());addCondition.await();// 该条件判断如果线程检测到队列已满,则全部进入等待。} catch (InterruptedException e) {e.printStackTrace();}}if (addPosition == data.length) {// 判断如果add索引位置等于size,则索引位置需要从0开始算起addPosition = 0;}data[addPosition] = value;/* * 这里会有个疑问？会不会把当前的位置原有的值给覆盖？ * 不会，因为当前只有一个线程进来,当add lock释放前,先去通知take取值 */System.out.println("add:" + value + " add index:" + addPosition + " thread name:" + Thread.currentThread().getName());addPosition++;//更新当前索引位置count++;takeCondition.signalAll();//唤醒take线程} finally {lock.unlock();//线程解锁}}public Object take() {lock.lock();Object value = null;try {while (count == 0) {try {//System.out.println("take await thread:" + Thread.currentThread().getName());takeCondition.await();} catch (InterruptedException e) {e.printStackTrace();}}if (takePosition == data.length) {takePosition = 0;}value = data[takePosition];System.out.println("take:" + value + " take index:" + takePosition + " thread name:" + Thread.currentThread().getName());takePosition++;count--;addCondition.signalAll();} finally {lock.unlock();}return value;}/* * Test main */public static void main(String[] args) {final BlockingQueue blockingQueue = new BlockingQueue(2);/* * 开启5个线程同时往阻塞队列里面赋值。 * 因为阻塞队列里面size=1,所以开启5个线程每次只能有一个线程往里面add数据,其他4个线程必须在等待 */for (int i = 0; i < 1000; i++) {final int index = i;new Thread(){public void run() {double value = Math.random();// blockingQueue.add(index);};}.start();}/* * 为了在多线程并发情况下，观测add线程等待情况 * 休眠5s之后开启新的线程从阻塞队列里面take */try {//Thread.sleep(5000);} catch (Exception e) {e.printStackTrace();}new Thread(){public void run() {while (true) {// 从阻塞队列里面取值Object value = blockingQueue.take();}};}.start();}}