生产消费者4 - 实现一个基于优先级的传输队列【消费顺序是由优先级决定的而不是抵达时间】

深藏阁楼爱情的钟 2022-09-24 05:16 6阅读 0赞

## 实现一个基于优先级的传输队列 ##

Java 7 API 提供几种与并发应用相关的数据类型。从这里面，我们想来重点介绍以下2种数据类型：

*  LinkedTransferQueue：这个数据类型支持那些有生产者和消费者结构的程序。 在那些应用，你有一个或者多个数据生产者，一个或多个数据消费者和一个被生产者和消费者共享的数据类型。生产者把数据放入数据结构内，然后消费者从数据结构内提取数据。如果数据结构为空，消费者会被阻塞直到有数据可以消费。如果数据结构满了，生产者就会被阻塞直到有空位来放数据。
 *  PriorityBlockingQueue：在这个数据结构，元素是按照顺序储存的。元素们必须实现 带有 compareTo() 方法的 Comparable 接口。当你在结构中插入数据时，它会与数据元素对比直到找到它的位置。

LinkedTransferQueue 的元素是按照抵达顺序储存的，所以越早到的越先被消耗。你有可能需要开发 producer/ consumer 程序，它的消耗顺序是由优先级决定的而不是抵达时间。在这个指南，你将学习如何实现在 producer/ consumer 问题中使用的数据结构，这些元素将被按照他们的优先级排序，级别高的会先被消耗。

## 实例代码 ##

package com.packtpub.java7.concurrency.chapter7.recipe09.core;
    
    import java.util.concurrent.TimeUnit;
    
    import com.packtpub.java7.concurrency.chapter7.recipe09.task.Consumer;
    import com.packtpub.java7.concurrency.chapter7.recipe09.task.Event;
    import com.packtpub.java7.concurrency.chapter7.recipe09.task.MyPriorityTransferQueue;
    import com.packtpub.java7.concurrency.chapter7.recipe09.task.Producer;
    
    /** * Main class of the example. * */
    public class Main {
    
        /** * @param args */
        public static void main(String[] args) throws Exception{
    
            /* * Create a Prioriy Transfer Queue */
            MyPriorityTransferQueue<Event> buffer=new MyPriorityTransferQueue<>();
    
            /* * Create a Producer object */
            Producer producer=new Producer(buffer);
    
            /* * Launch 10 producers */
            Thread producerThreads[]=new Thread[10];
            for (int i=0; i<producerThreads.length; i++) { 
                producerThreads[i]=new Thread(producer);
                producerThreads[i].start();
            }
    
            /* * Create and launch the consumer */
            Consumer consumer=new Consumer(buffer);
            Thread consumerThread=new Thread(consumer);
            consumerThread.start();
    
            /* * Write in the console the actual consumer count */
            System.out.printf("Main: Buffer: Consumer count: %d\n",buffer.getWaitingConsumerCount());
    
            /* * Transfer an event to the consumer */
            Event myEvent=new Event("Core Event",0);
            buffer.transfer(myEvent);
            System.out.printf("Main: My Event has ben transfered.\n");
    
            /* * Wait for the finalization of the producers */
            for (int i=0; i<producerThreads.length; i++) { 
                producerThreads[i].join();
            }
    
            /* * Sleep the thread for one second */
            TimeUnit.SECONDS.sleep(1);
    
            /* * Write the actual consumer count */
            System.out.printf("Main: Buffer: Consumer count: %d\n",buffer.getWaitingConsumerCount());
    
            /* * Transfer another event */
            myEvent=new Event("Core Event 2",0);
            buffer.transfer(myEvent);
    
            /* * Wait for the finalization of the consumer */
            consumerThread.join();
    
            /* * Write a message indicating the end of the program */
            System.out.printf("Main: End of the program\n");
        }
    
    }

package com.packtpub.java7.concurrency.chapter7.recipe09.task;
    
    import java.util.concurrent.LinkedBlockingQueue;
    import java.util.concurrent.PriorityBlockingQueue;
    import java.util.concurrent.TimeUnit;
    import java.util.concurrent.TransferQueue;
    import java.util.concurrent.atomic.AtomicInteger;
    import java.util.concurrent.locks.ReentrantLock;
    
    /** * This class implements a priority based transfer queue. It extends the * PriorityBlockingQueue class and implements the TransferQueue interface * * @param <E> Class of the elements to be stored in the queue */
    public class MyPriorityTransferQueue<E> extends PriorityBlockingQueue<E> implements
            TransferQueue<E> {
    
        /** * Serial Version of the class */
        private static final long serialVersionUID = 1L;
    
        /** * Number of consumers waiting */
        private AtomicInteger counter;
    
        /** * Blocking queue to store the transfered elements */
        private LinkedBlockingQueue<E> transfered;
    
        /** * Lock to control the acces to the operations */
        private ReentrantLock lock;
    
        /** * Constructor of the class */
        public MyPriorityTransferQueue() {
            counter=new AtomicInteger(0);
            lock=new ReentrantLock();
            transfered=new LinkedBlockingQueue<>();
        }
    
        /** * This method tries to transfer an element to a consumer. If there is * a consumer waiting, we puts the element in the queue and return the * true value. Else, return the false value. */
        @Override
        public boolean tryTransfer(E e) {
            lock.lock();
            boolean value;
            if (counter.get()==0) {
                value=false;
            } else {
                put(e);
                value=true;
            }
            lock.unlock();
            return value;
        }
    
        /** * Transfer an element to the consumer. If there is a consumer waiting, * puts the element on the queue and return the true value. Else, puts the * value in the transfered queue and returns the false value. In this case, the * thread than makes the call will be blocked until a consumer takes the transfered * elements */
        @Override
        public void transfer(E e) throws InterruptedException {
            lock.lock();
            if (counter.get()!=0) {
                put(e);
                lock.unlock();
            } else {
                transfered.add(e);
                lock.unlock();
                synchronized (e) {
                    e.wait();
                }
            }
        }
    
        /** * This method tries to transfer an element to a consumer waiting a maximum period * of time. If there is a consumer waiting, puts the element in the queue. Else, * puts the element in the queue of transfered elements and wait the specified period of time * until that time pass or the thread is interrupted. */
        @Override
        public boolean tryTransfer(E e, long timeout, TimeUnit unit)
                throws InterruptedException {
            lock.lock();
            if (counter.get()!=0) {
                put(e);
                lock.unlock();
                return true;
            } else {
                transfered.add(e);
                long newTimeout=TimeUnit.MILLISECONDS.convert(timeout, unit);
                lock.unlock();
                e.wait(newTimeout);
                lock.lock();
                if (transfered.contains(e)) {
                    transfered.remove(e);
                    lock.unlock();
                    return false;
                } else {
                    lock.unlock();
                    return true;
                }
            }
        }
    
    
        /** * Method that returns if the queue has waiting consumers */
        @Override
        public boolean hasWaitingConsumer() {
            return (counter.get()!=0);
        }
    
        /** * Method that returns the number of waiting consumers */
        @Override
        public int getWaitingConsumerCount() {
            return counter.get();
        }
    
        /** * Method that returns the first element of the queue or is blocked if the queue * is empty. If there is transfered elements, takes the first transfered element and * wake up the thread that is waiting for the transfer of that element. Else, takes the * first element of the queue or is blocked until there is one element in the queue. */
        @Override
        public E take() throws InterruptedException {
            lock.lock();
            counter.incrementAndGet();
            E value=transfered.poll();
            if (value==null) {
                lock.unlock();
                value=super.take();
                lock.lock();
            } else {
                synchronized (value) {
                    value.notify();
                }
            }
            counter.decrementAndGet();
            lock.unlock();
            return value;
        }
    }

package com.packtpub.java7.concurrency.chapter7.recipe09.task;
    
    /** * This class implements the producers of data. It store 100 * events in the queue with incremental priority * */
    public class Producer implements Runnable { 
    
        /** * Buffer used to store the events */
        private MyPriorityTransferQueue<Event> buffer;
    
        /** * Constructor of the class. It initializes its parameters * @param buffer Buffer to store the events */
        public Producer(MyPriorityTransferQueue<Event> buffer) {
            this.buffer=buffer;
        }
    
        /** * Main method of the producer. Store 100 events in the buffer with * incremental priority */
        @Override
        public void run() {
            for (int i=0; i<100; i++) {
                Event event=new Event(Thread.currentThread().getName(),i);
                buffer.put(event);
            }
        }
    
    }

package com.packtpub.java7.concurrency.chapter7.recipe09.task;
    
    /** * This class implements the Consumer of the events. There is only * one consumer in the example that consumes 1002 events * */
    public class Consumer implements Runnable { 
    
        /** * Buffer from which the consumer takes the events */
        private MyPriorityTransferQueue<Event> buffer;
    
        /** * Constructor of the class. Initializes its attributes * @param buffer Buffer from which the consumer takes the events */
        public Consumer(MyPriorityTransferQueue<Event> buffer) {
            this.buffer=buffer;
        }
    
        /** * Main method of the consumer. It takes 1002 events from the buffer */
        @Override
        public void run() {
            for (int i=0; i<1002; i++) {
                try {
                    Event value=buffer.take();
                    System.out.printf("Consumer: %s: %d\n",value.getThread(),value.getPriority());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    
    }

## 结果 ##

例子的主类创建了一个 MyPriorityTransferQueue 对象，10个生产者，和一个消费者，然后使用MyPriorityTransferQueue buffer 的 transfer() 方法来传输2个事件到 buffer。

你可以发现有着高级别的事件如何先被消费，和一个消费者如何消费传输的事件。

> Main: Buffer: Consumer count: 0  
> Consumer: Thread-7: 99  
> Consumer: Core Event: 0  
> Consumer: Thread-5: 99  
> Consumer: Thread-8: 99  
> Consumer: Thread-0: 99  
> Consumer: Thread-9: 99  
> Consumer: Thread-2: 99  
> Consumer: Thread-1: 99  
> Consumer: Thread-4: 99  
> Consumer: Thread-3: 99  
> Consumer: Thread-6: 99  
> Consumer: Thread-7: 98  
> Consumer: Thread-8: 98  
> Consumer: Thread-5: 98  
> Consumer: Thread-0: 98  
> Consumer: Thread-2: 98  
> Consumer: Thread-9: 98  
> Consumer: Thread-1: 98  
> Consumer: Thread-4: 98  
> Main: My Event has ben transfered.  
> Consumer: Thread-3: 98  
> Consumer: Thread-6: 98  
> Consumer: Thread-7: 97  
> Consumer: Thread-5: 97  
> Consumer: Thread-8: 97  
> Consumer: Thread-0: 97  
> Consumer: Thread-9: 97  
> Consumer: Thread-2: 97  
> Consumer: Thread-1: 97  
> Consumer: Thread-4: 97  
> Consumer: Thread-3: 97  
> Consumer: Thread-6: 97  
> Consumer: Thread-7: 96  
> Consumer: Thread-5: 96  
> Consumer: Thread-8: 96  
> Consumer: Thread-0: 96  
> Consumer: Thread-9: 96  
> Consumer: Thread-2: 96  
> Consumer: Thread-1: 96  
> Consumer: Thread-4: 96  
> Consumer: Thread-3: 96  
> Consumer: Thread-6: 96  
> Consumer: Thread-7: 95  
> Consumer: Thread-5: 95  
> Consumer: Thread-8: 95  
> Consumer: Thread-0: 95  
> Consumer: Thread-9: 95  
> Consumer: Thread-2: 95  
> Consumer: Thread-1: 95  
> Consumer: Thread-4: 95  
> Consumer: Thread-3: 95  
> Consumer: Thread-6: 95  
> Consumer: Thread-5: 94  
> Consumer: Thread-7: 94  
> Consumer: Thread-6: 94  
> Consumer: Thread-8: 94  
> Consumer: Thread-0: 94  
> Consumer: Thread-9: 94  
> Consumer: Thread-2: 94  
> Consumer: Thread-1: 94  
> Consumer: Thread-4: 94  
> Consumer: Thread-3: 94  
> Consumer: Thread-7: 93  
> Consumer: Thread-5: 93  
> Consumer: Thread-8: 93  
> Consumer: Thread-0: 93  
> Consumer: Thread-9: 93  
> Consumer: Thread-2: 93  
> Consumer: Thread-1: 93  
> Consumer: Thread-4: 93  
> Consumer: Thread-3: 93  
> Consumer: Thread-6: 93  
> Consumer: Thread-5: 92  
> Consumer: Thread-7: 92  
> Consumer: Thread-8: 92  
> Consumer: Thread-0: 92  
> Consumer: Thread-9: 92  
> Consumer: Thread-2: 92  
> Consumer: Thread-1: 92  
> Consumer: Thread-4: 92  
> Consumer: Thread-3: 92  
> Consumer: Thread-6: 92  
> Consumer: Thread-5: 91  
> Consumer: Thread-7: 91  
> Consumer: Thread-8: 91  
> Consumer: Thread-0: 91  
> Consumer: Thread-9: 91  
> Consumer: Thread-2: 91  
> Consumer: Thread-1: 91  
> Consumer: Thread-4: 91  
> Consumer: Thread-3: 91  
> Consumer: Thread-6: 91  
> Consumer: Thread-5: 90  
> Consumer: Thread-7: 90  
> Consumer: Thread-8: 90  
> Consumer: Thread-0: 90  
> Consumer: Thread-9: 90  
> Consumer: Thread-2: 90  
> Consumer: Thread-1: 90  
> Consumer: Thread-4: 90  
> Consumer: Thread-3: 90  
> Consumer: Thread-6: 90  
> Consumer: Thread-5: 89  
> Consumer: Thread-0: 89  
> Consumer: Thread-7: 89  
> Consumer: Thread-8: 89  
> Consumer: Thread-9: 89  
> Consumer: Thread-2: 89  
> Consumer: Thread-1: 89  
> Consumer: Thread-4: 89  
> Consumer: Thread-3: 89  
> Consumer: Thread-6: 89  
> Consumer: Thread-5: 88  
> Consumer: Thread-0: 88  
> Consumer: Thread-7: 88  
> Consumer: Thread-8: 88  
> Consumer: Thread-6: 88  
> Consumer: Thread-9: 88  
> Consumer: Thread-2: 88  
> Consumer: Thread-1: 88  
> Consumer: Thread-4: 88  
> Consumer: Thread-3: 88  
> Consumer: Thread-5: 87  
> Consumer: Thread-0: 87  
> Consumer: Thread-7: 87  
> Consumer: Thread-8: 87  
> Consumer: Thread-9: 87  
> Consumer: Thread-2: 87  
> Consumer: Thread-1: 87  
> Consumer: Thread-4: 87  
> Consumer: Thread-6: 87  
> Consumer: Thread-3: 87  
> Consumer: Thread-5: 86  
> Consumer: Thread-0: 86  
> Consumer: Thread-7: 86  
> Consumer: Thread-8: 86  
> Consumer: Thread-9: 86  
> Consumer: Thread-2: 86  
> Consumer: Thread-1: 86  
> Consumer: Thread-4: 86  
> Consumer: Thread-3: 86  
> Consumer: Thread-6: 86  
> Consumer: Thread-5: 85  
> Consumer: Thread-0: 85  
> Consumer: Thread-7: 85  
> Consumer: Thread-8: 85  
> Consumer: Thread-9: 85  
> Consumer: Thread-2: 85  
> Consumer: Thread-1: 85  
> Consumer: Thread-4: 85  
> Consumer: Thread-3: 85  
> Consumer: Thread-6: 85  
> Consumer: Thread-5: 84  
> Consumer: Thread-0: 84  
> Consumer: Thread-2: 84  
> Consumer: Thread-7: 84  
> Consumer: Thread-8: 84  
> Consumer: Thread-9: 84  
> Consumer: Thread-1: 84  
> Consumer: Thread-6: 84  
> Consumer: Thread-4: 84  
> Consumer: Thread-3: 84  
> Consumer: Thread-7: 83  
> Consumer: Thread-5: 83  
> Consumer: Thread-0: 83  
> Consumer: Thread-2: 83  
> Consumer: Thread-8: 83  
> Consumer: Thread-9: 83  
> Consumer: Thread-1: 83  
> Consumer: Thread-4: 83  
> Consumer: Thread-6: 83  
> Consumer: Thread-3: 83  
> Consumer: Thread-0: 82  
> Consumer: Thread-7: 82  
> Consumer: Thread-5: 82  
> Consumer: Thread-2: 82  
> Consumer: Thread-1: 82  
> Consumer: Thread-8: 82  
> Consumer: Thread-9: 82  
> Consumer: Thread-4: 82  
> Consumer: Thread-3: 82  
> Consumer: Thread-6: 82  
> Consumer: Thread-0: 81  
> Consumer: Thread-5: 81  
> Consumer: Thread-7: 81  
> Consumer: Thread-2: 81  
> Consumer: Thread-1: 81  
> Consumer: Thread-8: 81  
> Consumer: Thread-9: 81  
> Consumer: Thread-4: 81  
> Consumer: Thread-3: 81  
> Consumer: Thread-6: 81  
> Consumer: Thread-0: 80  
> Consumer: Thread-5: 80  
> Consumer: Thread-2: 80  
> Consumer: Thread-7: 80  
> Consumer: Thread-1: 80  
> Consumer: Thread-8: 80  
> Consumer: Thread-9: 80  
> Consumer: Thread-4: 80  
> Consumer: Thread-3: 80  
> Consumer: Thread-6: 80  
> Consumer: Thread-0: 79  
> Consumer: Thread-5: 79  
> Consumer: Thread-2: 79  
> Consumer: Thread-7: 79  
> Consumer: Thread-1: 79  
> Consumer: Thread-8: 79  
> Consumer: Thread-6: 79  
> Consumer: Thread-9: 79  
> Consumer: Thread-4: 79  
> Consumer: Thread-3: 79  
> Consumer: Thread-0: 78  
> Consumer: Thread-2: 78  
> Consumer: Thread-5: 78  
> Consumer: Thread-7: 78  
> Consumer: Thread-1: 78  
> Consumer: Thread-4: 78  
> Consumer: Thread-8: 78  
> Consumer: Thread-9: 78  
> Consumer: Thread-3: 78  
> Consumer: Thread-6: 78  
> Consumer: Thread-0: 77  
> Consumer: Thread-5: 77  
> Consumer: Thread-7: 77  
> Consumer: Thread-1: 77  
> Consumer: Thread-8: 77  
> Consumer: Thread-2: 77  
> Consumer: Thread-9: 77  
> Consumer: Thread-4: 77  
> Consumer: Thread-3: 77  
> Consumer: Thread-6: 77  
> Consumer: Thread-0: 76  
> Consumer: Thread-5: 76  
> Consumer: Thread-7: 76  
> Consumer: Thread-1: 76  
> Consumer: Thread-8: 76  
> Consumer: Thread-9: 76  
> Consumer: Thread-2: 76  
> Consumer: Thread-4: 76  
> Consumer: Thread-3: 76  
> Consumer: Thread-6: 76  
> Consumer: Thread-0: 75  
> Consumer: Thread-5: 75  
> Consumer: Thread-7: 75  
> Consumer: Thread-1: 75  
> Consumer: Thread-8: 75  
> Consumer: Thread-9: 75  
> Consumer: Thread-2: 75  
> Consumer: Thread-4: 75  
> Consumer: Thread-3: 75  
> Consumer: Thread-6: 75  
> Consumer: Thread-0: 74  
> Consumer: Thread-5: 74  
> Consumer: Thread-7: 74  
> Consumer: Thread-1: 74  
> Consumer: Thread-8: 74  
> Consumer: Thread-9: 74  
> Consumer: Thread-4: 74  
> Consumer: Thread-3: 74  
> Consumer: Thread-2: 74  
> Consumer: Thread-6: 74  
> Consumer: Thread-0: 73  
> Consumer: Thread-5: 73  
> Consumer: Thread-7: 73  
> Consumer: Thread-1: 73  
> Consumer: Thread-8: 73  
> Consumer: Thread-9: 73  
> Consumer: Thread-4: 73  
> Consumer: Thread-3: 73  
> Consumer: Thread-6: 73  
> Consumer: Thread-2: 73  
> Consumer: Thread-0: 72  
> Consumer: Thread-5: 72  
> Consumer: Thread-7: 72  
> Consumer: Thread-1: 72  
> Consumer: Thread-8: 72  
> Consumer: Thread-6: 72  
> Consumer: Thread-9: 72  
> Consumer: Thread-2: 72  
> Consumer: Thread-4: 72  
> Consumer: Thread-3: 72  
> Consumer: Thread-0: 71  
> Consumer: Thread-7: 71  
> Consumer: Thread-1: 71  
> Consumer: Thread-8: 71  
> Consumer: Thread-2: 71  
> Consumer: Thread-3: 71  
> Consumer: Thread-9: 71  
> Consumer: Thread-4: 71  
> Consumer: Thread-6: 71  
> Consumer: Thread-5: 71  
> Consumer: Thread-0: 70  
> Consumer: Thread-7: 70  
> Consumer: Thread-1: 70  
> Consumer: Thread-8: 70  
> Consumer: Thread-2: 70  
> Consumer: Thread-9: 70  
> Consumer: Thread-4: 70  
> Consumer: Thread-3: 70  
> Consumer: Thread-6: 70  
> Consumer: Thread-5: 70  
> Consumer: Thread-0: 69  
> Consumer: Thread-7: 69  
> Consumer: Thread-1: 69  
> Consumer: Thread-8: 69  
> Consumer: Thread-2: 69  
> Consumer: Thread-9: 69  
> Consumer: Thread-4: 69  
> Consumer: Thread-3: 69  
> Consumer: Thread-6: 69  
> Consumer: Thread-5: 69  
> Consumer: Thread-0: 68  
> Consumer: Thread-7: 68  
> Consumer: Thread-2: 68  
> Consumer: Thread-1: 68  
> Consumer: Thread-8: 68  
> Consumer: Thread-4: 68  
> Consumer: Thread-5: 68  
> Consumer: Thread-9: 68  
> Consumer: Thread-6: 68  
> Consumer: Thread-3: 68  
> Consumer: Thread-0: 67  
> Consumer: Thread-1: 67  
> Consumer: Thread-7: 67  
> Consumer: Thread-2: 67  
> Consumer: Thread-8: 67  
> Consumer: Thread-9: 67  
> Consumer: Thread-5: 67  
> Consumer: Thread-4: 67  
> Consumer: Thread-3: 67  
> Consumer: Thread-6: 67  
> Consumer: Thread-0: 66  
> Consumer: Thread-1: 66  
> Consumer: Thread-2: 66  
> Consumer: Thread-7: 66  
> Consumer: Thread-8: 66  
> Consumer: Thread-9: 66  
> Consumer: Thread-5: 66  
> Consumer: Thread-4: 66  
> Consumer: Thread-3: 66  
> Consumer: Thread-6: 66  
> Consumer: Thread-0: 65  
> Consumer: Thread-1: 65  
> Consumer: Thread-2: 65  
> Consumer: Thread-7: 65  
> Consumer: Thread-6: 65  
> Consumer: Thread-8: 65  
> Consumer: Thread-9: 65  
> Consumer: Thread-5: 65  
> Consumer: Thread-4: 65  
> Consumer: Thread-3: 65  
> Consumer: Thread-0: 64  
> Consumer: Thread-1: 64  
> Consumer: Thread-7: 64  
> Consumer: Thread-2: 64  
> Consumer: Thread-8: 64  
> Consumer: Thread-9: 64  
> Consumer: Thread-5: 64  
> Consumer: Thread-4: 64  
> Consumer: Thread-3: 64  
> Consumer: Thread-6: 64  
> Consumer: Thread-0: 63  
> Consumer: Thread-1: 63  
> Consumer: Thread-2: 63  
> Consumer: Thread-7: 63  
> Consumer: Thread-8: 63  
> Consumer: Thread-9: 63  
> Consumer: Thread-4: 63  
> Consumer: Thread-3: 63  
> Consumer: Thread-6: 63  
> Consumer: Thread-5: 63  
> Consumer: Thread-0: 62  
> Consumer: Thread-4: 62  
> Consumer: Thread-2: 62  
> Consumer: Thread-7: 62  
> Consumer: Thread-8: 62  
> Consumer: Thread-9: 62  
> Consumer: Thread-3: 62  
> Consumer: Thread-5: 62  
> Consumer: Thread-6: 62  
> Consumer: Thread-1: 62  
> Consumer: Thread-2: 61  
> Consumer: Thread-0: 61  
> Consumer: Thread-7: 61  
> Consumer: Thread-8: 61  
> Consumer: Thread-9: 61  
> Consumer: Thread-4: 61  
> Consumer: Thread-3: 61  
> Consumer: Thread-6: 61  
> Consumer: Thread-5: 61  
> Consumer: Thread-1: 61  
> Consumer: Thread-0: 60  
> Consumer: Thread-2: 60  
> Consumer: Thread-7: 60  
> Consumer: Thread-8: 60  
> Consumer: Thread-9: 60  
> Consumer: Thread-4: 60  
> Consumer: Thread-3: 60  
> Consumer: Thread-6: 60  
> Consumer: Thread-5: 60  
> Consumer: Thread-1: 60  
> Consumer: Thread-0: 59  
> Consumer: Thread-2: 59  
> Consumer: Thread-7: 59  
> Consumer: Thread-4: 59  
> Consumer: Thread-9: 59  
> Consumer: Thread-3: 59  
> Consumer: Thread-1: 59  
> Consumer: Thread-8: 59  
> Consumer: Thread-6: 59  
> Consumer: Thread-5: 59  
> Consumer: Thread-0: 58  
> Consumer: Thread-2: 58  
> Consumer: Thread-7: 58  
> Consumer: Thread-4: 58  
> Consumer: Thread-5: 58  
> Consumer: Thread-8: 58  
> Consumer: Thread-9: 58  
> Consumer: Thread-3: 58  
> Consumer: Thread-6: 58  
> Consumer: Thread-1: 58  
> Consumer: Thread-0: 57  
> Consumer: Thread-2: 57  
> Consumer: Thread-7: 57  
> Consumer: Thread-4: 57  
> Consumer: Thread-8: 57  
> Consumer: Thread-9: 57  
> Consumer: Thread-5: 57  
> Consumer: Thread-1: 57  
> Consumer: Thread-3: 57  
> Consumer: Thread-6: 57  
> Consumer: Thread-0: 56  
> Consumer: Thread-2: 56  
> Consumer: Thread-7: 56  
> Consumer: Thread-3: 56  
> Consumer: Thread-4: 56  
> Consumer: Thread-8: 56  
> Consumer: Thread-1: 56  
> Consumer: Thread-9: 56  
> Consumer: Thread-5: 56  
> Consumer: Thread-6: 56  
> Consumer: Thread-0: 55  
> Consumer: Thread-2: 55  
> Consumer: Thread-7: 55  
> Consumer: Thread-4: 55  
> Consumer: Thread-8: 55  
> Consumer: Thread-9: 55  
> Consumer: Thread-3: 55  
> Consumer: Thread-5: 55  
> Consumer: Thread-1: 55  
> Consumer: Thread-6: 55  
> Consumer: Thread-0: 54  
> Consumer: Thread-2: 54  
> Consumer: Thread-7: 54  
> Consumer: Thread-1: 54  
> Consumer: Thread-6: 54  
> Consumer: Thread-4: 54  
> Consumer: Thread-8: 54  
> Consumer: Thread-9: 54  
> Consumer: Thread-3: 54  
> Consumer: Thread-5: 54  
> Consumer: Thread-0: 53  
> Consumer: Thread-2: 53  
> Consumer: Thread-7: 53  
> Consumer: Thread-4: 53  
> Consumer: Thread-9: 53  
> Consumer: Thread-3: 53  
> Consumer: Thread-8: 53  
> Consumer: Thread-5: 53  
> Consumer: Thread-6: 53  
> Consumer: Thread-1: 53  
> Consumer: Thread-0: 52  
> Consumer: Thread-2: 52  
> Consumer: Thread-7: 52  
> Consumer: Thread-4: 52  
> Consumer: Thread-3: 52  
> Consumer: Thread-8: 52  
> Consumer: Thread-9: 52  
> Consumer: Thread-6: 52  
> Consumer: Thread-5: 52  
> Consumer: Thread-1: 52  
> Consumer: Thread-0: 51  
> Consumer: Thread-2: 51  
> Consumer: Thread-7: 51  
> Consumer: Thread-8: 51  
> Consumer: Thread-3: 51  
> Consumer: Thread-9: 51  
> Consumer: Thread-6: 51  
> Consumer: Thread-5: 51  
> Consumer: Thread-1: 51  
> Consumer: Thread-4: 51  
> Consumer: Thread-0: 50  
> Consumer: Thread-2: 50  
> Consumer: Thread-7: 50  
> Consumer: Thread-3: 50  
> Consumer: Thread-4: 50  
> Consumer: Thread-1: 50  
> Consumer: Thread-8: 50  
> Consumer: Thread-9: 50  
> Consumer: Thread-5: 50  
> Consumer: Thread-6: 50  
> Consumer: Thread-0: 49  
> Consumer: Thread-2: 49  
> Consumer: Thread-7: 49  
> Consumer: Thread-3: 49  
> Consumer: Thread-9: 49  
> Consumer: Thread-4: 49  
> Consumer: Thread-8: 49  
> Consumer: Thread-1: 49  
> Consumer: Thread-6: 49  
> Consumer: Thread-5: 49  
> Consumer: Thread-0: 48  
> Consumer: Thread-2: 48  
> Consumer: Thread-7: 48  
> Consumer: Thread-3: 48  
> Consumer: Thread-9: 48  
> Consumer: Thread-4: 48  
> Consumer: Thread-8: 48  
> Consumer: Thread-6: 48  
> Consumer: Thread-5: 48  
> Consumer: Thread-1: 48  
> Consumer: Thread-4: 47  
> Consumer: Thread-7: 47  
> Consumer: Thread-3: 47  
> Consumer: Thread-9: 47  
> Consumer: Thread-0: 47  
> Consumer: Thread-2: 47  
> Consumer: Thread-5: 47  
> Consumer: Thread-6: 47  
> Consumer: Thread-1: 47  
> Consumer: Thread-8: 47  
> Consumer: Thread-7: 46  
> Consumer: Thread-9: 46  
> Consumer: Thread-1: 46  
> Consumer: Thread-4: 46  
> Consumer: Thread-5: 46  
> Consumer: Thread-8: 46  
> Consumer: Thread-2: 46  
> Consumer: Thread-6: 46  
> Consumer: Thread-0: 46  
> Consumer: Thread-3: 46  
> Consumer: Thread-7: 45  
> Consumer: Thread-9: 45  
> Consumer: Thread-5: 45  
> Consumer: Thread-4: 45  
> Consumer: Thread-8: 45  
> Consumer: Thread-0: 45  
> Consumer: Thread-1: 45  
> Consumer: Thread-6: 45  
> Consumer: Thread-2: 45  
> Consumer: Thread-3: 45  
> Consumer: Thread-7: 44  
> Consumer: Thread-8: 44  
> Consumer: Thread-4: 44  
> Consumer: Thread-5: 44  
> Consumer: Thread-3: 44  
> Consumer: Thread-9: 44  
> Consumer: Thread-2: 44  
> Consumer: Thread-0: 44  
> Consumer: Thread-6: 44  
> Consumer: Thread-1: 44  
> Consumer: Thread-8: 43  
> Consumer: Thread-7: 43  
> Consumer: Thread-9: 43  
> Consumer: Thread-0: 43  
> Consumer: Thread-4: 43  
> Consumer: Thread-1: 43  
> Consumer: Thread-6: 43  
> Consumer: Thread-3: 43  
> Consumer: Thread-5: 43  
> Consumer: Thread-2: 43  
> Consumer: Thread-7: 42  
> Consumer: Thread-4: 42  
> Consumer: Thread-3: 42  
> Consumer: Thread-0: 42  
> Consumer: Thread-8: 42  
> Consumer: Thread-9: 42  
> Consumer: Thread-5: 42  
> Consumer: Thread-1: 42  
> Consumer: Thread-6: 42  
> Consumer: Thread-2: 42  
> Consumer: Thread-7: 41  
> Consumer: Thread-4: 41  
> Consumer: Thread-8: 41  
> Consumer: Thread-1: 41  
> Consumer: Thread-5: 41  
> Consumer: Thread-0: 41  
> Consumer: Thread-9: 41  
> Consumer: Thread-6: 41  
> Consumer: Thread-3: 41  
> Consumer: Thread-2: 41  
> Consumer: Thread-7: 40  
> Consumer: Thread-1: 40  
> Consumer: Thread-4: 40  
> Consumer: Thread-8: 40  
> Consumer: Thread-2: 40  
> Consumer: Thread-5: 40  
> Consumer: Thread-0: 40  
> Consumer: Thread-6: 40  
> Consumer: Thread-9: 40  
> Consumer: Thread-3: 40  
> Consumer: Thread-7: 39  
> Consumer: Thread-9: 39  
> Consumer: Thread-6: 39  
> Consumer: Thread-4: 39  
> Consumer: Thread-8: 39  
> Consumer: Thread-3: 39  
> Consumer: Thread-5: 39  
> Consumer: Thread-0: 39  
> Consumer: Thread-1: 39  
> Consumer: Thread-2: 39  
> Consumer: Thread-7: 38  
> Consumer: Thread-8: 38  
> Consumer: Thread-5: 38  
> Consumer: Thread-9: 38  
> Consumer: Thread-2: 38  
> Consumer: Thread-3: 38  
> Consumer: Thread-0: 38  
> Consumer: Thread-1: 38  
> Consumer: Thread-6: 38  
> Consumer: Thread-4: 38  
> Consumer: Thread-7: 37  
> Consumer: Thread-9: 37  
> Consumer: Thread-2: 37  
> Consumer: Thread-5: 37  
> Consumer: Thread-1: 37  
> Consumer: Thread-8: 37  
> Consumer: Thread-6: 37  
> Consumer: Thread-4: 37  
> Consumer: Thread-0: 37  
> Consumer: Thread-3: 37  
> Consumer: Thread-7: 36  
> Consumer: Thread-9: 36  
> Consumer: Thread-6: 36  
> Consumer: Thread-8: 36  
> Consumer: Thread-1: 36  
> Consumer: Thread-3: 36  
> Consumer: Thread-5: 36  
> Consumer: Thread-0: 36  
> Consumer: Thread-4: 36  
> Consumer: Thread-2: 36  
> Consumer: Thread-7: 35  
> Consumer: Thread-2: 35  
> Consumer: Thread-0: 35  
> Consumer: Thread-9: 35  
> Consumer: Thread-1: 35  
> Consumer: Thread-6: 35  
> Consumer: Thread-8: 35  
> Consumer: Thread-5: 35  
> Consumer: Thread-4: 35  
> Consumer: Thread-3: 35  
> Consumer: Thread-9: 34  
> Consumer: Thread-7: 34  
> Consumer: Thread-4: 34  
> Consumer: Thread-8: 34  
> Consumer: Thread-2: 34  
> Consumer: Thread-1: 34  
> Consumer: Thread-0: 34  
> Consumer: Thread-5: 34  
> Consumer: Thread-6: 34  
> Consumer: Thread-3: 34  
> Consumer: Thread-3: 33  
> Consumer: Thread-7: 33  
> Consumer: Thread-2: 33  
> Consumer: Thread-0: 33  
> Consumer: Thread-8: 33  
> Consumer: Thread-6: 33  
> Consumer: Thread-5: 33  
> Consumer: Thread-9: 33  
> Consumer: Thread-1: 33  
> Consumer: Thread-4: 33  
> Consumer: Thread-8: 32  
> Consumer: Thread-7: 32  
> Consumer: Thread-0: 32  
> Consumer: Thread-2: 32  
> Consumer: Thread-5: 32  
> Consumer: Thread-3: 32  
> Consumer: Thread-9: 32  
> Consumer: Thread-6: 32  
> Consumer: Thread-4: 32  
> Consumer: Thread-1: 32  
> Consumer: Thread-0: 31  
> Consumer: Thread-7: 31  
> Consumer: Thread-9: 31  
> Consumer: Thread-8: 31  
> Consumer: Thread-1: 31  
> Consumer: Thread-6: 31  
> Consumer: Thread-5: 31  
> Consumer: Thread-3: 31  
> Consumer: Thread-2: 31  
> Consumer: Thread-4: 31  
> Consumer: Thread-8: 30  
> Consumer: Thread-7: 30  
> Consumer: Thread-0: 30  
> Consumer: Thread-3: 30  
> Consumer: Thread-6: 30  
> Consumer: Thread-1: 30  
> Consumer: Thread-5: 30  
> Consumer: Thread-4: 30  
> Consumer: Thread-9: 30  
> Consumer: Thread-2: 30  
> Consumer: Thread-8: 29  
> Consumer: Thread-7: 29  
> Consumer: Thread-0: 29  
> Consumer: Thread-6: 29  
> Consumer: Thread-5: 29  
> Consumer: Thread-9: 29  
> Consumer: Thread-3: 29  
> Consumer: Thread-2: 29  
> Consumer: Thread-4: 29  
> Consumer: Thread-1: 29  
> Consumer: Thread-8: 28  
> Consumer: Thread-7: 28  
> Consumer: Thread-0: 28  
> Consumer: Thread-3: 28  
> Consumer: Thread-4: 28  
> Consumer: Thread-5: 28  
> Consumer: Thread-1: 28  
> Consumer: Thread-6: 28  
> Consumer: Thread-2: 28  
> Consumer: Thread-9: 28  
> Consumer: Thread-7: 27  
> Consumer: Thread-9: 27  
> Consumer: Thread-0: 27  
> Consumer: Thread-5: 27  
> Consumer: Thread-6: 27  
> Consumer: Thread-1: 27  
> Consumer: Thread-4: 27  
> Consumer: Thread-8: 27  
> Consumer: Thread-3: 27  
> Consumer: Thread-2: 27  
> Consumer: Thread-7: 26  
> Consumer: Thread-6: 26  
> Consumer: Thread-1: 26  
> Consumer: Thread-9: 26  
> Consumer: Thread-4: 26  
> Consumer: Thread-5: 26  
> Consumer: Thread-0: 26  
> Consumer: Thread-3: 26  
> Consumer: Thread-2: 26  
> Consumer: Thread-8: 26  
> Consumer: Thread-7: 25  
> Consumer: Thread-8: 25  
> Consumer: Thread-6: 25  
> Consumer: Thread-2: 25  
> Consumer: Thread-0: 25  
> Consumer: Thread-4: 25  
> Consumer: Thread-1: 25  
> Consumer: Thread-3: 25  
> Consumer: Thread-9: 25  
> Consumer: Thread-5: 25  
> Consumer: Thread-9: 24  
> Consumer: Thread-0: 24  
> Consumer: Thread-3: 24  
> Consumer: Thread-7: 24  
> Consumer: Thread-2: 24  
> Consumer: Thread-4: 24  
> Consumer: Thread-6: 24  
> Consumer: Thread-5: 24  
> Consumer: Thread-1: 24  
> Consumer: Thread-8: 24  
> Consumer: Thread-0: 23  
> Consumer: Thread-8: 23  
> Consumer: Thread-5: 23  
> Consumer: Thread-3: 23  
> Consumer: Thread-2: 23  
> Consumer: Thread-1: 23  
> Consumer: Thread-4: 23  
> Consumer: Thread-9: 23  
> Consumer: Thread-6: 23  
> Consumer: Thread-7: 23  
> Consumer: Thread-0: 22  
> Consumer: Thread-1: 22  
> Consumer: Thread-6: 22  
> Consumer: Thread-9: 22  
> Consumer: Thread-5: 22  
> Consumer: Thread-2: 22  
> Consumer: Thread-3: 22  
> Consumer: Thread-4: 22  
> Consumer: Thread-7: 22  
> Consumer: Thread-8: 22  
> Consumer: Thread-7: 21  
> Consumer: Thread-5: 21  
> Consumer: Thread-3: 21  
> Consumer: Thread-9: 21  
> Consumer: Thread-0: 21  
> Consumer: Thread-4: 21  
> Consumer: Thread-6: 21  
> Consumer: Thread-1: 21  
> Consumer: Thread-2: 21  
> Consumer: Thread-8: 21  
> Consumer: Thread-7: 20  
> Consumer: Thread-3: 20  
> Consumer: Thread-8: 20  
> Consumer: Thread-9: 20  
> Consumer: Thread-5: 20  
> Consumer: Thread-1: 20  
> Consumer: Thread-2: 20  
> Consumer: Thread-6: 20  
> Consumer: Thread-4: 20  
> Consumer: Thread-0: 20  
> Consumer: Thread-3: 19  
> Consumer: Thread-9: 19  
> Consumer: Thread-8: 19  
> Consumer: Thread-5: 19  
> Consumer: Thread-2: 19  
> Consumer: Thread-7: 19  
> Consumer: Thread-4: 19  
> Consumer: Thread-6: 19  
> Consumer: Thread-1: 19  
> Consumer: Thread-0: 19  
> Consumer: Thread-3: 18  
> Consumer: Thread-7: 18  
> Consumer: Thread-4: 18  
> Consumer: Thread-6: 18  
> Consumer: Thread-1: 18  
> Consumer: Thread-8: 18  
> Consumer: Thread-0: 18  
> Consumer: Thread-2: 18  
> Consumer: Thread-5: 18  
> Consumer: Thread-9: 18  
> Consumer: Thread-1: 17  
> Consumer: Thread-3: 17  
> Consumer: Thread-2: 17  
> Consumer: Thread-9: 17  
> Consumer: Thread-5: 17  
> Consumer: Thread-6: 17  
> Consumer: Thread-7: 17  
> Consumer: Thread-4: 17  
> Consumer: Thread-0: 17  
> Consumer: Thread-8: 17  
> Consumer: Thread-5: 16  
> Consumer: Thread-3: 16  
> Consumer: Thread-2: 16  
> Consumer: Thread-7: 16  
> Consumer: Thread-6: 16  
> Consumer: Thread-4: 16  
> Consumer: Thread-8: 16  
> Consumer: Thread-9: 16  
> Consumer: Thread-0: 16  
> Consumer: Thread-1: 16  
> Consumer: Thread-6: 15  
> Consumer: Thread-9: 15  
> Consumer: Thread-0: 15  
> Consumer: Thread-1: 15  
> Consumer: Thread-8: 15  
> Consumer: Thread-7: 15  
> Consumer: Thread-5: 15  
> Consumer: Thread-3: 15  
> Consumer: Thread-2: 15  
> Consumer: Thread-4: 15  
> Consumer: Thread-8: 14  
> Consumer: Thread-7: 14  
> Consumer: Thread-5: 14  
> Consumer: Thread-4: 14  
> Consumer: Thread-9: 14  
> Consumer: Thread-0: 14  
> Consumer: Thread-6: 14  
> Consumer: Thread-1: 14  
> Consumer: Thread-3: 14  
> Consumer: Thread-2: 14  
> Consumer: Thread-4: 13  
> Consumer: Thread-5: 13  
> Consumer: Thread-0: 13  
> Consumer: Thread-7: 13  
> Consumer: Thread-1: 13  
> Consumer: Thread-9: 13  
> Consumer: Thread-2: 13  
> Consumer: Thread-6: 13  
> Consumer: Thread-3: 13  
> Consumer: Thread-8: 13  
> Consumer: Thread-1: 12  
> Consumer: Thread-0: 12  
> Consumer: Thread-9: 12  
> Consumer: Thread-2: 12  
> Consumer: Thread-7: 12  
> Consumer: Thread-3: 12  
> Consumer: Thread-6: 12  
> Consumer: Thread-8: 12  
> Consumer: Thread-4: 12  
> Consumer: Thread-5: 12  
> Consumer: Thread-4: 11  
> Consumer: Thread-9: 11  
> Consumer: Thread-1: 11  
> Consumer: Thread-2: 11  
> Consumer: Thread-6: 11  
> Consumer: Thread-7: 11  
> Consumer: Thread-0: 11  
> Consumer: Thread-3: 11  
> Consumer: Thread-8: 11  
> Consumer: Thread-5: 11  
> Consumer: Thread-5: 10  
> Consumer: Thread-8: 10  
> Consumer: Thread-7: 10  
> Consumer: Thread-0: 10  
> Consumer: Thread-9: 10  
> Consumer: Thread-3: 10  
> Consumer: Thread-1: 10  
> Consumer: Thread-4: 10  
> Consumer: Thread-2: 10  
> Consumer: Thread-6: 10  
> Consumer: Thread-8: 9  
> Consumer: Thread-2: 9  
> Consumer: Thread-9: 9  
> Consumer: Thread-7: 9  
> Consumer: Thread-4: 9  
> Consumer: Thread-1: 9  
> Consumer: Thread-6: 9  
> Consumer: Thread-3: 9  
> Consumer: Thread-5: 9  
> Consumer: Thread-0: 9  
> Consumer: Thread-2: 8  
> Consumer: Thread-0: 8  
> Consumer: Thread-8: 8  
> Consumer: Thread-7: 8  
> Consumer: Thread-9: 8  
> Consumer: Thread-3: 8  
> Consumer: Thread-4: 8  
> Consumer: Thread-6: 8  
> Consumer: Thread-1: 8  
> Consumer: Thread-5: 8  
> Consumer: Thread-6: 7  
> Consumer: Thread-4: 7  
> Consumer: Thread-0: 7  
> Consumer: Thread-7: 7  
> Consumer: Thread-8: 7  
> Consumer: Thread-5: 7  
> Consumer: Thread-1: 7  
> Consumer: Thread-2: 7  
> Consumer: Thread-9: 7  
> Consumer: Thread-3: 7  
> Consumer: Thread-1: 6  
> Consumer: Thread-6: 6  
> Consumer: Thread-3: 6  
> Consumer: Thread-5: 6  
> Consumer: Thread-8: 6  
> Consumer: Thread-9: 6  
> Consumer: Thread-7: 6  
> Consumer: Thread-0: 6  
> Consumer: Thread-4: 6  
> Consumer: Thread-2: 6  
> Consumer: Thread-5: 5  
> Consumer: Thread-1: 5  
> Consumer: Thread-8: 5  
> Consumer: Thread-2: 5  
> Consumer: Thread-6: 5  
> Consumer: Thread-3: 5  
> Consumer: Thread-7: 5  
> Consumer: Thread-9: 5  
> Consumer: Thread-4: 5  
> Consumer: Thread-0: 5  
> Consumer: Thread-5: 4  
> Consumer: Thread-2: 4  
> Consumer: Thread-9: 4  
> Consumer: Thread-3: 4  
> Consumer: Thread-6: 4  
> Consumer: Thread-7: 4  
> Consumer: Thread-8: 4  
> Consumer: Thread-0: 4  
> Consumer: Thread-1: 4  
> Consumer: Thread-4: 4  
> Consumer: Thread-8: 3  
> Consumer: Thread-1: 3  
> Consumer: Thread-9: 3  
> Consumer: Thread-6: 3  
> Consumer: Thread-7: 3  
> Consumer: Thread-0: 3  
> Consumer: Thread-4: 3  
> Consumer: Thread-5: 3  
> Consumer: Thread-3: 3  
> Consumer: Thread-2: 3  
> Consumer: Thread-6: 2  
> Consumer: Thread-2: 2  
> Consumer: Thread-9: 2  
> Consumer: Thread-7: 2  
> Consumer: Thread-1: 2  
> Consumer: Thread-8: 2  
> Consumer: Thread-5: 2  
> Consumer: Thread-0: 2  
> Consumer: Thread-3: 2  
> Consumer: Thread-4: 2  
> Consumer: Thread-6: 1  
> Consumer: Thread-0: 1  
> Consumer: Thread-2: 1  
> Consumer: Thread-8: 1  
> Consumer: Thread-5: 1  
> Consumer: Thread-1: 1  
> Consumer: Thread-3: 1  
> Consumer: Thread-9: 1  
> Consumer: Thread-4: 1  
> Consumer: Thread-7: 1  
> Consumer: Thread-5: 0  
> Consumer: Thread-8: 0  
> Consumer: Thread-3: 0  
> Consumer: Thread-1: 0  
> Consumer: Thread-2: 0  
> Consumer: Thread-6: 0  
> Consumer: Thread-4: 0  
> Consumer: Thread-7: 0  
> Consumer: Thread-0: 0  
> Consumer: Thread-9: 0  
> Main: Buffer: Consumer count: 1  
> Consumer: Core Event 2: 0  
> Main: End of the program

## 原理 ##

在这个指南，你已经实现了 MyPriorityTransferQueue 数据结构。这个数据类型是在 producer/consumer 问题中使用的，它的元素是按照优先级排列的。由于 Java 不支持多个继承，所以你首先要决定的是 MyPriorityTransferQueue 类的基类。你扩展了 PriorityBlockingQueue 类，来实现在结构中插入数据按照优先级排序。你也实现了 TransferQueue 接口，添加了与 producer/consumer 相关的3个方法。

MyPriortyTransferQueue 类有以下2个属性：

1.  AtomicInteger 属性，名为 counter: 此属性储存了正在等待从数据类型提取元素的消费者的数量。当一个消费者调用 take()操作来从数据类型中提取元素时，counter 数增加。当消费者结束 take() 操作的执行时，counter 数再次增加。在 hasWaitingConsumer() 和 getWaitingConsumerCount() 方法的实现中使用到了 counter。
2.  ReentrantLock 属性，名为 lock: 此属性是用来控制访问已实现的操作。只有一个线程可以用数据类型。最后一个，LinkedBlockingQueue list 用来储存传输的元素。

在 MyPriorityTransferQueue 中，你实现了一些方法。全部方法都在 TransferQueue 接口中声明了和在PriorityBlockingQueue 接口实现的 take() 方法。在之前已经描述了2个方法了。来看看剩下的方法的描述：

*  tryTransfer(E e): 此方法尝试直接发送元素给消费者。如果有消费者在等待，此方法储存元素到 priority queue 中为了立刻提供给消费者，并返回 true 值。如果没有消费者在等待，方法返回 false 值。
 *  transfer(E e): 此方法直接发送元素给消费者。如果有消费者在等待，此方法储存元素到 priority queue 中为了立刻提供给消费者。

否则，把元素储存到已传输的元素list 并阻塞线程直到元素被消耗。当线程进入休眠时，你要释放锁，如果不的话，你就阻塞了queue。

*  tryTransfer(E e, long timeout, TimeUnit unit): 此方法与 transfer() 方法相似，只是它的线程被阻塞的时间段是由参数决定的。当线程进入休眠时，你要释放锁，如果不的话，你就阻塞了queue。
 *  take(): 此方法返回下一个要被消耗的元素。如果在 transferred 元素list中有元素，就从list中取走元素。否则，就从 priority queue 中取元素。

一旦你实现了数据类型，你就实现了 Event 类。它就是在数据类型里储存的元素构成的类。Event 类有2个属性用来储存生产者的ID和事件的优先级，并实现了 Comparable 接口，为了满足你的数据类型的需要。

接着，你实现了 Producer 和 Consumer 类。在这个例子中，你有 10 个生产者和一个消费者，他们共享同一个 buffer。每个生产者生成100个事件，他们的优先级是递增的， 所以有高优先级的事件在越后面才生成。

转自： [ifeve][]

[ifeve]: http://ifeve.com/customizing-concurrency-classes-11-2/