在run方法中使用同步块很奇怪

Question

package multithreading.concurrency.cp.bqueue;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

class Producer implements Runnable {

    private final BlockingQueue<Object> queue;

    private int priority;

    public Producer(int priority, BlockingQueue<Object> queue) {
        this.priority = priority;
        this.queue = queue;
    }

    @Override
    public void run() {
        while (true) {
            try {
                Thread.sleep(priority);
                synchronized (this) {
                    queue.put("object");
                    System.out.println("put  " + queue.size());
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

class Consumer implements Runnable {

    private final BlockingQueue<Object> queue;

    private int priority;

    public Consumer(int priority, BlockingQueue<Object> queue) {
        this.priority = priority;
        this.queue = queue;
    }

    @Override
    public void run() {
        while (true) {
            try {
                Thread.sleep(priority);
                synchronized (this) {
                    queue.take();
                    System.out.println("take " + queue.size());
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class ConsumerProducer {

    private static final int SHARED_BUFFER_CAPACITY = 10;

    public static void main(String[] args) {

        BlockingQueue<Object> sharedBuffer = new LinkedBlockingQueue<Object>(SHARED_BUFFER_CAPACITY);

        new Thread(new Producer(200, sharedBuffer)).start();
        new Thread(new Producer(300, sharedBuffer)).start();
        new Thread(new Consumer(1000, sharedBuffer)).start();
        new Thread(new Consumer(1000, sharedBuffer)).start();
    }
}

为什么我无法在run方法中获得像synced block这样的输出，所以不起作用：

take 9
put  10
take 9
take 9
put  10
put  10
take 9
put  10
take 9
put  10
take 9
take 8

？

Answer 1

您为什么要同步“ this”？ 您实际上是在4个不同的互斥对象上进行同步（“ this”是指生产者或消费者的实际实例）。 尝试使用synchronized(queue)