java - Java中与BlockingQueue进行线程同步

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                7年前关闭。
            
        

我是BlockingQueue概念的新手，给人的印象是它不需要使用wait（）和notify（）。我编写了以下代码作为线程同步的初步测试（为清楚起见，省略了一些代码）：

q = new LinkedBlockingQueue<flight>();

generator = new EventGenerator(q,flight);
southwest = new Airline(q);

new Thread(generator).start();
new Thread(southwest).start();

与生产者类EventGenerator。 EventGenerator从初始状态（SC）出发经过所有状态，直到到达登机门AG：

import java.util.concurrent.BlockingQueue;

public class EventGenerator implements Runnable
{
private final BlockingQueue<flight> bqueue;
private final flight f;

EventGenerator(BlockingQueue<flight> q, flight f1)
{
    bqueue = q;
    f = f1;
}

public void run()
{
    try
    {
        while (f.state != "AG") { bqueue.put(produce()); }
    }
    catch (InterruptedException ex)
    {
        System.out.println(ex);
        System.exit(0);
    }
}

flight produce()
{
    if (f.state.equals("SC")){ f.state = "BD"; }
    else if (f.state.equals("BD")) { f.state = "LG"; }
    else if (f.state.equals("LG")) { f.state = "TO"; }
    else if (f.state.equals("TO")) { f.state = "LD"; }
    else if (f.state.equals("LD")) { f.state = "AG"; }

    return f;
}

消费类航空公司将接收航班状态的每项更改，并进行打印：

import java.util.concurrent.BlockingQueue;

public class Airline implements Runnable
{
    private final BlockingQueue<flight> bqueue;

    Airline(BlockingQueue<flight> q)
    {
        bqueue = q;
    }

public void run()
{
    try
    {
        while (!bqueue.isEmpty()) { consume(bqueue.take());}
    }
    catch (InterruptedException ex)
    {
        System.out.println(ex);
        System.exit(0);
    }
}

void consume(flight f)
{
    System.out.println("Flight no. " + f.flightno + " is now in state " + f.state);
}
}

该项目编译并运行没有错误。但是，我期望（并希望）结果达到以下目的：

Flight no. 1 is now in state SC
Flight no. 1 is now in state BD
Flight no. 1 is now in state LG
Flight no. 1 is now in state TO
Flight no. 1 is now in state LD
Flight no. 1 is now in state AG

但是，相反，我几乎总是得到：

Flight no. 1 is now in state AG
Flight no. 1 is now in state AG
Flight no. 1 is now in state AG
Flight no. 1 is now in state AG
Flight no. 1 is now in state AG

我是否错误地实现了BlockingQueue？

最佳答案

您目前遇到的问题实际上是produce方法。您正在更改同一对象的状态，并将其多次放置在队列中。您实际上想要做的是将修改后的副本放入队列。如果您的Flight对象是不可变的，那么您将不会遇到此问题。

除上述以外，this answer对于while循环中的条件问题也很正确。

关于java - Java中与BlockingQueue进行线程同步，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/15013856/