【发布时间】：2016-06-07 15:47:53
【问题描述】：
刚开始学习多线程。我在多个线程中有 5 个生产者和 2 个消费者。基本上，这个程序将 100 个项目添加到队列中。当队列大小为100时，生产者将停止添加。我希望消费者在消费者从队列中删除所有项目时通知生产者，以便生产者可以重新开始添加。目前生产者会等待，但永远不会收到消费者的通知。
制作人：
public class Producer implements Runnable {
private BlockingQueue sharedQueue;
private final int queueSize;
private Object lock = new Object();
public Producer(BlockingQueue sharedQueue, int queueSize){
this.sharedQueue = sharedQueue;
this.queueSize = queueSize;
}
public void run() {
while(true) {
if(sharedQueue.size()== queueSize){
try {
synchronized (lock) {
sharedQueue.wait();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
try {
sharedQueue.put("Producer: " + sharedQueue.size());
Thread.sleep(500);
System.out.println("Producer: Queue Size " + sharedQueue.size() + " Current Thread " + Thread.currentThread());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
消费者：
public class Consumer implements Runnable{
private BlockingQueue sharedQueue;
private final int queueSize;
private final int queueEmpty=0;
private Object lock = new Object();
public Consumer(BlockingQueue sharedQueue, int queueSize){
this.sharedQueue = sharedQueue;
this.queueSize = queueSize;
}
//Notify awaiting thread if the sharedQueue is empty
public void run() {
while (true) {
if(sharedQueue.size()==queueEmpty){
synchronized (lock) {
this.notifyAll();
}
}
try {
sharedQueue.take();
Thread.sleep(800);
System.out.println("Consumer: Queue Size " + sharedQueue.size() + " Current Thread" + Thread.currentThread());
}catch(InterruptedException e){
e.printStackTrace();
}
}
}
}
主类
public class App{
//A simple program to illustrate how producer and consumer pattern works with blocking queue using executor service
public static void main( String[] args )
{
final BlockingQueue<String> sharedQueue = new ArrayBlockingQueue<String> (100);
final int queueSize =100;
final int producerNum = 5;
final int consumerNum = 2;
final ExecutorService executorProducer = Executors.newFixedThreadPool(producerNum);
final ExecutorService executorConsumer = Executors.newFixedThreadPool(consumerNum);
for(int i=0;i<producerNum;i++){
Producer producer = new Producer(sharedQueue,queueSize);
executorProducer.execute(producer);
}
for(int j=0;j<consumerNum;j++){
Consumer consumer = new Consumer(sharedQueue,queueSize);
executorConsumer.execute(consumer);
}
}
}
【问题讨论】：
-
您认为
this.notifyAll();会做什么？你为什么这么认为？ -
如果 notifyAll 被调用，这段代码应该抛出 IllegalMonitorStateException。
-
我认为 notifyAll 会唤醒所有等待这个对象的线程。在当前线程放弃对该对象的锁定之前，被唤醒的线程将无法继续。所以我的错误是等待和通知需要在同一个对象上使用？
-
这里有多个错误。阅读有关受保护块的 Oracle 教程应该可以教会您一些东西。
-
我告诉过你有多个问题。阅读 oracle 教程：docs.oracle.com/javase/tutorial/essential/concurrency/…
标签： java multithreading wait producer-consumer notify