阻塞队列的简单实现

阻塞队列的简单实现

阻塞队列是一种当队列满了和队列空了时，会阻塞的队列，简单的实现如下，实现了添加元素的操作(put)和取元素的操作(take)，这里用到了JUC下的Condition和ReentrantLock类

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Created by CvShrimp on 2017/7/19.
 */
public class BlockingQueue {
    final Lock lock = new ReentrantLock();
    final Condition full = lock.newCondition();
    final Condition empty = lock.newCondition();
    //设置存放元素的Object数组，最多存放30个元素
    final Object[] items = new Object[30];
    //放置元素的位置
    int putptr;
    //取元素的位置
    int takeptr;
    //队列中元素的个数，当达到队列的最大长度(这里是30)或者0时，分别会阻塞put或者take操作，当满足put或者take的条件时，会自动唤醒相应的线程
    int count;

    public void put(Object o) {
        lock.lock();
        System.out.println("lock the put");
        try {
            if(count == items.length) {
                System.out.println("Full, blocking put");
                try {
                    full.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            items[putptr] = o;
            count++;
            if(++putptr == items.length) {
                putptr = 0;
            }
            System.out.println("put item success");
            //唤醒由于队列空了，阻塞在empty上的线程
            empty.signal();
        } finally {
            System.out.println("unlock the put");
            lock.unlock();
        }
    }

    public Object take() {
        lock.lock();
        System.out.println("lock the take");
        try {
            if(count == 0) {
                try {
                    empty.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            Object o = items[takeptr];
            count--;
            if(++takeptr == items.length) {
                takeptr = 0;
            }
            //唤醒由于队列满了，阻塞在full上的线程
            full.signal();
            return o;
        } finally {
            System.out.println("unlock the take");
            lock.unlock();
        }
    }

    public boolean isEmpty() {
        return count == 0;
    }

    public static void main(String[] args) {
        BlockingQueue blockQueue = new BlockingQueue();
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                blockQueue.put("Lelouch");
                blockQueue.put("Zero");
                blockQueue.put("CvShrimp");
                System.out.println(blockQueue.take());
                System.out.println(blockQueue.take());
            }
        };

        Runnable runnable1 = new Runnable() {
            @Override
            public void run() {
                System.out.println(blockQueue.take());
            }
        };

        ExecutorService threadPool = Executors.newCachedThreadPool();
        threadPool.execute(runnable);
        threadPool.execute(runnable1);

    }
}