-1

我正在编写一个使用多线程概念在 Java 中实现生产者消费者问题的程序。以下是我应该如何做的一些细节:

1) 主线程应该创建一个缓冲区,其容量指定为命令行参数。生产者和消费者线程的数量也被指定为命令行参数。我应该为每个生产者和消费者线程分配一个唯一的编号。如何为生产者和消费者线程分配唯一编号?

2)生产者线程在无限循环中运行。它生成具有以下格式的数据项(字符串):<producer number>_<data item number>. 例如,来自线程号 1 的第一个数据项将是 1_1,来自线程号 3 的第二个数据项将是 3_2。如何以这种格式创建数据项?

3)然后Producer线程将一个条目写入生产者日志文件(<生产者编号>“已生成” <data item>)。在写入日志条目时,它会尝试插入缓冲区。如果插入成功,它会在日志文件中创建一个条目(<producer number> <data item>“插入成功”)。我该如何编写这样的代码?

下面是我写的Java代码。

import java.util.*;
import java.util.logging.*;

public class PC2
{
    public static void main(String args[])
    {
            ArrayList<Integer> queue = new ArrayList<Integer>();

            int size = Integer.parseInt(args[2]);
            Thread[] prod = new Thread[Integer.parseInt(args[0])];
            Thread[] cons = new Thread[Integer.parseInt(args[1])];

            for(int i=0; i<prod.length; i++)
            {
                    prod[i] = new Thread(new Producer(queue, size));
                    prod[i].start();
            }

            for(int i=0; i<cons.length; i++)
            {
                    cons[i] = new Thread(new Consumer(queue, size));
                    cons[i].start();
                }

    }
}

class Producer extends Thread
{
    private final ArrayList<Integer> queue;
    private final int size;

    public Producer(ArrayList<Integer> queue, int size)
    {
            this.queue = queue;
            this.size = size;
    }

    public void run()
    {
            while(true){
            for(int i=0; i<size; i++)
            {
                    System.out.println("Produced: "+i+" by id " +Thread.currentThread().getId());
try
                    {
                            produce(i);
                            Thread.sleep(3000);
                    }
                    catch(Exception e)
                    {
                            Logger.getLogger(Producer.class.getName()).log(Level.SEVERE, null, e);
                    }
            }}
    }


    public void produce(int i) throws InterruptedException
    {
            while(queue.size() == size)
            {
                    synchronized(queue)
                    {
                            System.out.println("Queue is full "+Thread.currentThread().getName() +" is waiting, size: "+queue.size());
                            queue.wait();
                       }
            }
            synchronized(queue)
            {
                    queue.add(i);
                    queue.notifyAll();
            }
    }
}

class Consumer extends Thread
{
    private final ArrayList<Integer> queue;
    private final int size;

    public Consumer(ArrayList<Integer> queue, int size)
    {
            this.queue = queue;
            this.size = size;
    }

    public void run()
    {
            while(true)
            {
                    try
                    {       System.out.println("Consumed: "+consume());
                            Thread.sleep(1000);
                    }
                    catch(Exception e)
                    {
                            Logger.getLogger(Consumer.class.getName()).log(Level.SEVERE, null, e);
                    }
            }
    }

    public int consume() throws InterruptedException
    {
            while(queue.isEmpty())
            {
                    synchronized(queue)
                    {
                            System.out.println("Queue is empty "+Thread.currentThread().getName()+" is waiting, size: "+queue.size());
                            queue.wait();
                        }
            }

            synchronized (queue)
            {
                    queue.notifyAll();
                    System.out.println("Consumed by id "+Thread.currentThread().getId());
                    return (Integer) queue.remove(0);

            }
    }
}

如何执行上述步骤?

4

5 回答 5

1

对于生产者消费者问题,最好的解决方案是 BlockingQueue。我正在测试一些东西,因此设计了相同类型的程序,现在根据您的需要对其进行了修改。

看看有没有帮助。

import java.util.concurrent.*;
public class ThreadingExample {

    public static void main(String args[]){
        BlockingQueue<Message> blockingQueue = new ArrayBlockingQueue<Message>(100);
        ExecutorService exec = Executors.newCachedThreadPool();
        exec.execute(new Producer(blockingQueue));
        exec.execute(new Consumer(blockingQueue));
    }

}
class Message{
    private static int count=0;
    int messageId;
    Message(){
        this.messageId=count++;
        System.out.print("message Id"+messageId+" Created ");
    }
}
class Producer implements Runnable{

    private BlockingQueue<Message> blockingQueue;
    Producer(BlockingQueue<Message> blockingQueue){
        this.blockingQueue=blockingQueue;
    }

    @Override
    public void run(){
        while(!Thread.interrupted()){
            System.out.print("Producer Started");
            try {
                blockingQueue.put(new Message());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("Producer Done");
        }
    }
}

class Consumer implements Runnable{
    private BlockingQueue<Message> blockingQueue;
    Consumer(BlockingQueue<Message> blockingQueue){
        this.blockingQueue=blockingQueue;
    }

    @Override
    public void run(){
        while(!Thread.interrupted()){
            System.out.print("Concumer Started");
            try{
                Message message  = blockingQueue.take();
                System.out.print("message Id"+message.messageId+" Consumed ");
            }
            catch(InterruptedException e){
                e.printStackTrace();
            }
            System.out.println("Concumer Done");
        }
    }
}
于 2013-10-31T16:11:53.400 回答
1

我应该为每个生产者和消费者线程分配一个唯一的编号。如何为生产者和消费者线程分配唯一编号?

向生产者/消费者类添加一个实例(非静态)变量。初始化新的生产者/消费者对象时,传入唯一编号。你可以跟踪你在int counter主班上的号码。

2)生产者线程在无限循环中运行。它生成具有以下格式的数据项(字符串):<生产者编号>_<数据项编号>。例如,来自线程号 1 的第一个数据项将是 1_1,来自线程号 3 的第二个数据项将是 3_2。如何以这种格式创建数据项?

使用同步方法和/或原子变量。查看 Java Concurrency

3)然后Producer线程向生产者日志文件中写入一个条目(<生产者编号>“已生成”<数据项>)。在写入日志条目时,它会尝试插入缓冲区。如果插入成功,它会在日志文件中创建一个条目(<生产者编号><数据项>“插入成功”)。我该如何编写这样的代码?

我的回答和上一个问题一样:阅读 Java 并发。花一个小时阅读有关同步、锁和原子变量的知识,我保证你会很容易地编写你的程序。

于 2013-10-31T01:49:19.280 回答
0

我尝试了以下可能对您有用的方法,除了 3 上的缓冲区条件,您可以自己添加部分代码。希望这可以帮助。

public class Message {

    private String msg;

    public Message(String msg) {
        super();
        this.msg = msg;
    }

    public String getMsg(){
        return msg;
    }
}




import java.util.concurrent.BlockingQueue;

public class Producer implements Runnable {

    private BlockingQueue<Message> queue;
    private boolean run = true;

    public Producer(BlockingQueue<Message> queue) {
        super();
        this.queue = queue;
    }

    public void setRun(boolean val) {
        this.run = val;
    }

    @Override
    public void run() {
        int i = 0;
        while (run) {
            Message msg = new Message(Thread.currentThread().getName() + "_"+ i);
            try {
                Thread.sleep(i * 100);
                queue.put(msg);
                System.out.println("Producer: "+Thread.currentThread().getName()+" produced and added to the queue: "+msg.getMsg());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            i++;
            if(i==10){
                setRun(false);
                System.out.println(Thread.currentThread().getName()+" stopped");
            }
        }

    }
}



import java.util.concurrent.BlockingQueue;

public class Consumer implements Runnable{

    private BlockingQueue<Message> queue;
    private boolean run = true;

    public Consumer(BlockingQueue<Message> queue) {
        super();
        this.queue = queue;
    }

    public void setRun(boolean val){
        this.run = val;
    }

    @Override
    public void run() {
        while(run){
            try {
                Thread.sleep(100);
                Message msg = queue.take();
                System.out.println("Consumer: "+Thread.currentThread().getName()+"         generated/consumed "+msg.getMsg());
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }

    }
  }




import java.util.Scanner;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

public class ProducerConsumerMain {

    public static void main(String[] args) {
        System.out
                .println("please enter the number of producer:consumer:size of the queue in order");

        Scanner scan = new Scanner(System.in);

        Thread[] prodThreads = new Thread[scan.nextInt()];
        Thread[] consThreads = new Thread[scan.nextInt()];
        BlockingQueue<Message> queue = new ArrayBlockingQueue<Message>(scan.nextInt());

        for (int i = 0; i < prodThreads.length; i++) {
            prodThreads[i] = new Thread(new Producer(queue), "" + i);
            prodThreads[i].start();
        }

        for (int i = 0; i < consThreads.length; i++) {
            consThreads[i] = new Thread(new Consumer(queue), "" + i);
            consThreads[i].start();
        }


    }

}
于 2014-09-14T19:33:32.813 回答
0

请参考以下代码。您可以根据命令行参数更改常量值。我已经测试了代码,它可以按照您的要求工作。

import java.util.LinkedList;
import java.util.Queue;

public class ProducerConsumerProblem {
    public static int CAPACITY = 10; // At a time maximum of 10 tasks can be
                                        // produced.
    public static int PRODUCERS = 2;
    public static int CONSUMERS = 4;

    public static void main(String args[]) {
        Queue<String> mTasks = new LinkedList<String>();
        for (int i = 1; i <= PRODUCERS; i++) {
            Thread producer = new Thread(new Producer(mTasks));
            producer.setName("Producer " + i);
            producer.start();
        }
        for (int i = 1; i <= CONSUMERS; i++) {
            Thread consumer = new Thread(new Consumer(mTasks));
            consumer.setName("Consumer " + i);
            consumer.start();
        }

    }

}

class Producer implements Runnable {

    Queue<String> mSharedTasks;
    int taskCount = 1;

    public Producer(Queue<String> mSharedTasks) {
        super();
        this.mSharedTasks = mSharedTasks;
    }

    @Override
    public void run() {
        while (true) {
            synchronized (mSharedTasks) {
                try {
                    if (mSharedTasks.size() == ProducerConsumerProblem.CAPACITY) {
                        System.out.println("Producer Waiting!!");
                        mSharedTasks.wait();
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            while (mSharedTasks.size() != ProducerConsumerProblem.CAPACITY) {

                try {
                    Thread.sleep(50);
                } catch (InterruptedException e) {
                }

                String produceHere = Thread.currentThread().getName()
                        + "_Item number_" + taskCount++;

                synchronized (mSharedTasks) {
                    mSharedTasks.add(produceHere);
                    System.out.println(produceHere);
                    if (mSharedTasks.size() == 1) {
                        mSharedTasks.notifyAll(); // Informs consumer that there
                                                    // is something to consume.
                    }
                }
            }

        }
    }
}

class Consumer implements Runnable {
    Queue<String> mSharedTasks;

    public Consumer(Queue<String> mSharedTasks) {
        super();
        this.mSharedTasks = mSharedTasks;
    }

    @Override
    public void run() {
        while (true) {
            synchronized (mSharedTasks) {
                if (mSharedTasks.isEmpty()) { // Checks whether there is no task
                                                // to consume.
                    try {
                        mSharedTasks.wait(); // Waits for producer to produce!
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }

            }
            while (!mSharedTasks.isEmpty()) { // Consumes till task list is
                                                // empty
                try {
                    // Consumer consumes late hence producer has to wait...!
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                synchronized (mSharedTasks) {

                    System.out.println(Thread.currentThread().getName()
                            + " consumed " + mSharedTasks.poll());
                    if (mSharedTasks.size() == ProducerConsumerProblem.CAPACITY - 1)
                        mSharedTasks.notifyAll();
                }

            }

        }
    }

}
于 2015-07-03T12:06:36.610 回答
-1
public class ProducerConsumerTest {

    public static void main(String[] args) {
        CubbyHole c = new CubbyHole();
        Producer p1 = new Producer(c, 1);
        Consumer c1 = new Consumer(c, 1);
        p1.start();
        c1.start();
    }
}

class CubbyHole {

    private int contents;
    private boolean available = false;

    public synchronized int get() {
        while (available == false) {
            try {
                wait();
            } catch (InterruptedException e) {
            }
        }
        available = false;
        notifyAll();
        return contents;
    }

    public synchronized void put(int value) {
        while (available == true) {
            try {
                wait();
            } catch (InterruptedException e) {
            }
        }
        contents = value;
        available = true;
        notifyAll();
    }
}

class Consumer extends Thread {

    private CubbyHole cubbyhole;
    private int number;

    public Consumer(CubbyHole c, int number) {
        cubbyhole = c;
        this.number = number;
    }

    public void run() {
        int value = 0;
        for (int i = 0; i < 10; i++) {
            value = cubbyhole.get();
            System.out.println("Consumer #"
                    + this.number
                    + " got: " + value);
        }
    }
}

class Producer extends Thread {

    private CubbyHole cubbyhole;
    private int number;

    public Producer(CubbyHole c, int number) {
        cubbyhole = c;
        this.number = number;
    }

    public void run() {
        for (int i = 0; i < 10; i++) {
            cubbyhole.put(i);
            System.out.println("Producer #" + this.number
                    + " put: " + i);
            try {
                sleep((int) (Math.random() * 100));
            } catch (InterruptedException e) {
            }
        }
    }
}
于 2015-08-03T06:04:47.270 回答