在并发程序中从BlockingQueue获取对象的最佳方法？

Question

在没有遇到竞争条件的情况下,在并发程序中从BlockingQueue中获取对象的最佳方法是什么？我目前正在做以下事情,我不相信这是最好的方法:

BlockingQueue<Violation> vQueue;
/* 
in the constructor I pass in a BlockingQueue object 
full of violations that need to be processed - cut out for brevity
*/

Violation v;
while ( ( v = vQueue.poll(500, TimeUnit.MILLISECONDS) ) != null ) {
    // do stuff with the violation
}

我还没有达到竞争状态......但是,我不确定这是否真的安全.

Answer 1

class Producer implements Runnable {
   private final BlockingQueue queue;
   Producer(BlockingQueue q) { queue = q; }
   public void run() {
     try {
       while (true) { queue.put(produce()); }
     } catch (InterruptedException ex) { ... handle ...}
   }
   Object produce() { ... }
 }

 class Consumer implements Runnable {
   private final BlockingQueue queue;
   Consumer(BlockingQueue q) { queue = q; }
   public void run() {
     try {
       while (true) { consume(queue.take()); }
     } catch (InterruptedException ex) { ... handle ...}
   }
   void consume(Object x) { ... }
 }

 class Setup {
   void main() {
     BlockingQueue q = new SomeQueueImplementation();
     Producer p = new Producer(q);
     Consumer c1 = new Consumer(q);
     Consumer c2 = new Consumer(q);
     new Thread(p).start();
     new Thread(c1).start();
     new Thread(c2).start();
   }
 }

这个例子取自JDK 1.6文档BlockingQueue.所以你可以看到你正在以正确的方式做到这一点.这是引用它告诉你它必须工作的引用:

内存一致性效果:与其他并发集合一样,在将对象放入BlockingQueue之前,线程中的操作发生在从另一个线程中的BlockingQueue访问或删除该元素之后的操作之前.