[Java Concurrent] 多线程合作 producer-consumers / queue 的简单案例

在多线程环境下，通过 BlockingQueue，实现生产者-消费者场景。

Toast 被生产和消费的对象。

ToastQueue 继承了 LinkedblockingQueue ，用于中间存储 Toast 。

Producer 生产 Toast ，并将生产出来的 Toast 放进队列 initialToastQ 中。

Processor 加工 Toast，从 initialToastQ 中获得生产出来的 Toast，将其加工并放进队列 finishedToast 中。

Consumer 消费 Toast，从 finishedToastQ 中获得加工完成的 Toast。

ThreadHelper 工具类，用于输出线程相关信息。

ProducerConsumerDemo 演示这个场景

代码实现：

Toast 实现

public class Toast {

    private int id;

    public Toast(int id){
        this.id = id;
    }

    public String toString(){
        return " toast#" + id;
    }
}

ToastQueue 实现

import java.util.concurrent.LinkedBlockingQueue;

public class ToastQueue extends LinkedBlockingQueue<Toast> {
    private static final long serialVersionUID = 1L;
}

Producer 循环生产 Toast

import java.util.concurrent.TimeUnit;

public class Producer implements Runnable {

    private ToastQueue toastQueue;
    private int count;

    public Producer(ToastQueue toastQueue){
        this.toastQueue = toastQueue;
        this.count = 0;
    }

    @Override
    public void run() {
        try {
            while (true){
                TimeUnit.MILLISECONDS.sleep(100);

                Toast toast = new Toast(count);
                count++;
                toastQueue.put(toast);
                ThreadHelper.print(" produced " + toast);
            }
        }catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Processor 从 intialToastQ 获得 Toast ，对其加工，并放进 finishedToastQ 中。

import java.util.concurrent.TimeUnit;

public class Processor implements Runnable {

    private ToastQueue initialToastQ;
    private ToastQueue finishedToastQ;

    public Processor(ToastQueue initialToastQ, ToastQueue finishedToastQ){
        this.initialToastQ = initialToastQ;
        this.finishedToastQ = finishedToastQ;
    }

    @Override
    public void run() {
        try {
            while (true){
                Toast toast = initialToastQ.take();

                ThreadHelper.print(" processing " + toast);

                TimeUnit.MILLISECONDS.sleep(180);

                finishedToastQ.put(toast);
            }
        }catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Consumer 消耗 Toast

public class Consumer implements Runnable {

    private ToastQueue finishedToastQ;

    public Consumer(ToastQueue finishedToastQ){
        this.finishedToastQ = finishedToastQ;
    }

    @Override
    public void run() {
        try {
            while (true){
                Toast toast = finishedToastQ.take();
                ThreadHelper.print(" consumed " + toast);
            }
        }catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

ThreadHelper 线程帮助类

public class ThreadHelper {
    public static void print(String msg){
        System.out.println("[" + Thread.currentThread().getName() + " ] " + msg);
    }
}

演示烤面包的生产、加工、消费的场景

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class ProducerConsumerDemo {

    public static void main() throws InterruptedException{

        ToastQueue initialToastQ = new ToastQueue();
        ToastQueue finishedToastQ = new ToastQueue();

        ExecutorService exec = Executors.newCachedThreadPool();
        exec.execute(new Producer(initialToastQ));
        exec.execute(new Processor(initialToastQ, finishedToastQ));
        exec.execute(new Consumer(finishedToastQ));

        TimeUnit.SECONDS.sleep(2);
        exec.shutdownNow();
    }
}

输出结果：

[pool-1-thread-2 ]  processing  toast#0
[pool-1-thread-1 ]  produced  toast#0
[pool-1-thread-1 ]  produced  toast#1
[pool-1-thread-2 ]  processing  toast#1
[pool-1-thread-3 ]  consumed  toast#0
[pool-1-thread-1 ]  produced  toast#2
[pool-1-thread-1 ]  produced  toast#3
[pool-1-thread-2 ]  processing  toast#2
[pool-1-thread-3 ]  consumed  toast#1
[pool-1-thread-1 ]  produced  toast#4
[pool-1-thread-1 ]  produced  toast#5
[pool-1-thread-2 ]  processing  toast#3
[pool-1-thread-3 ]  consumed  toast#2
[pool-1-thread-1 ]  produced  toast#6
[pool-1-thread-1 ]  produced  toast#7
[pool-1-thread-2 ]  processing  toast#4
[pool-1-thread-3 ]  consumed  toast#3
[pool-1-thread-1 ]  produced  toast#8
[pool-1-thread-2 ]  processing  toast#5
[pool-1-thread-3 ]  consumed  toast#4
[pool-1-thread-1 ]  produced  toast#9
[pool-1-thread-1 ]  produced  toast#10
[pool-1-thread-2 ]  processing  toast#6
[pool-1-thread-3 ]  consumed  toast#5
[pool-1-thread-1 ]  produced  toast#11
[pool-1-thread-1 ]  produced  toast#12
[pool-1-thread-2 ]  processing  toast#7
[pool-1-thread-3 ]  consumed  toast#6
[pool-1-thread-1 ]  produced  toast#13
[pool-1-thread-1 ]  produced  toast#14
[pool-1-thread-2 ]  processing  toast#8
[pool-1-thread-3 ]  consumed  toast#7
[pool-1-thread-1 ]  produced  toast#15
[pool-1-thread-1 ]  produced  toast#16
[pool-1-thread-2 ]  processing  toast#9
[pool-1-thread-3 ]  consumed  toast#8
[pool-1-thread-1 ]  produced  toast#17
[pool-1-thread-2 ]  processing  toast#10
[pool-1-thread-3 ]  consumed  toast#9
[pool-1-thread-1 ]  produced  toast#18
java.lang.InterruptedException
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.reportInterruptAfterWait(AbstractQueuedSynchronizer.java:2014)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2048)
    at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
    at concurrencyProducerConsumer.Consumer.run(Consumer.java:15)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
java.lang.InterruptedException: sleep interrupted
    at java.lang.Thread.sleep(Native Method)
    at java.lang.Thread.sleep(Thread.java:340)
    at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)
    at concurrencyProducerConsumer.Producer.run(Producer.java:19)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
java.lang.InterruptedException: sleep interrupted
    at java.lang.Thread.sleep(Native Method)
    at java.lang.Thread.sleep(Thread.java:340)
    at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)
    at concurrencyProducerConsumer.Processor.run(Processor.java:24)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

参考资料

Page 868, Produer-consumers and queue, Thinking in Java