2016-10-22 120 views
-2

我在下面章节23.6 Proceducer /消费者关系的一个例子:ArrayBlockingQueue(“爪哇 - 如何编程10日)为什么ArrayBlockingQueue对象的大小没有更新?

我试图运行的例子,但我不明白为什么‘buffer.size()’不更新的开始。

我的确在消费类稍加修改。我把300米的毫秒为Thread.sleep(Generator.nextInt(300))。 这里是我的结果。

Producer writes 1 Buffer cells occupied: 0 
Consumer reads 1 Buffer cells occupied: 0 
Producer writes 2 Buffer cells occupied: 1 
Consumer reads 2 Buffer cells occupied: 0 
Producer writes 3 Buffer cells occupied: 1 
Consumer reads 3 Buffer cells occupied: 0 
Producer writes 4 Buffer cells occupied: 1 
Consumer reads 4 Buffer cells occupied: 0 
Producer writes 5 Buffer cells occupied: 1 
Consumer reads 5 Buffer cells occupied: 0 
Producer writes 6 Buffer cells occupied: 1 
Consumer reads 6 Buffer cells occupied: 0 
Producer writes 7 Buffer cells occupied: 1 
Consumer reads 7 Buffer cells occupied: 0 
Producer writes 8 Buffer cells occupied: 1 
Consumer reads 8 Buffer cells occupied: 0 
Producer writes 9 Buffer cells occupied: 1 
Consumer reads 9 Buffer cells occupied: 0 
Producer writes10 Buffer cells occupied: 1 
Producer done producing 
Terminating producer 
Consumer reads 10 Buffer cells occupied: 0 

Consumer reads values totaling 55 
Terminating Consumer 

这是代码。

public class BlockingBufferTest { 
public static void main(String[] args) throws InterruptedException { 
    ExecutorService executorService = Executors.newCachedThreadPool(); 

    BlockingBuffer sharedLocation = new BlockingBuffer(); 

    executorService.execute(new Producer(sharedLocation)); 
    executorService.execute(new Consumer(sharedLocation)); 

    executorService.shutdown(); 
    executorService.awaitTermination(1, TimeUnit.MINUTES); 

} // end main method 
} // end class 

public class BlockingBuffer implements Buffer { 

private final ArrayBlockingQueue<Integer> buffer; // shared buffer 

public BlockingBuffer() { 
    buffer = new ArrayBlockingQueue<>(1); 
} 
@Override 
public void blockingPut(int value) throws InterruptedException { 
    buffer.put(value); // place value in buffer 
    System.out.printf("%s%2d\t%s%d%n", "Producer writes", value, "Buffer cells occupied: ", buffer.size()); 
} 

@Override 
public int blockingGet() throws InterruptedException { 
    int readValue = buffer.take(); // remove value from buffer 
    System.out.printf("%s %2d\t%s%d%n", "Consumer reads", readValue, "Buffer cells occupied: ", buffer.size()); 
    return readValue; 
} 
} 

public class Consumer implements Runnable { 

private static final SecureRandom generator = new SecureRandom(); 
private final Buffer sharedLocation; // reference to shared object 

public Consumer(Buffer sharedLocation) { 
    this.sharedLocation = sharedLocation; 
} // end constructor 

// stores values 1 to 10 in sharedLocation 
@Override 
public void run() { 
    int sum = 0; 
    for(int count=1; count<=10; count++) { 
     try { 
      Thread.sleep(generator.nextInt(300));// random sleep 
      sum +=sharedLocation.blockingGet(); 

     } catch (InterruptedException e) { 
      Thread.currentThread().interrupt(); 
     } 
    } // end for 

    System.out.printf("%n%s %d%n%s%n","Consumer reads values totaling", sum, "Terminating Consumer"); 
} // end run method 
} 

public class Producer implements Runnable { 

private static final SecureRandom generator = new SecureRandom(); 
private final Buffer sharedLocation; // reference to shared object 

public Producer(Buffer sharedLocation) { 
    this.sharedLocation = sharedLocation; 
} // end constructor 

// stores values 1 to 10 in sharedLocation 
@Override 
public void run() { 
    int sum = 0; 
    for(int count=1; count<=10; count++) { 
     try { 
      Thread.sleep(generator.nextInt(3000));// random sleep 
      sharedLocation.blockingPut(count); 
      sum += count; 

     } catch (InterruptedException e) { 
      Thread.currentThread().interrupt(); 
     } 
    } // end for 

    System.out.printf("Producer done producing%nTerminating producer%n"); 
} // end run method 
} 

回答

0

这看起来像是线程排序/抢先式多任务的人工产物。

基本上生产者/消费者的每个周期都不是原子的。他们可以在一个周期中抢占对方。

这里例如如何操作的顺序可能的工作:

Producer thread: put value    (size=1) 
Consumer thread: read value    (size=0) 
Producer thread: x1 = buffer.size() --> x1 = 0 
Producer thread: print x1 --> you observe 'Producer writes 1 Buffer cells occupied: 0' 
Consumer thread: x2 = buffer.size() --> x2 = 0 
Consumer thread: print x --> you observe 'Consumer reads 1 Buffer cells occupied: 0' 

附:它实际上有点棘手,没有所有操作的线性排序,但只有一些组,但对于这个解释可以

+0

谢谢伊万。 :) – Hikaru

相关问题