Acabo de empezar a aprender multihilo. Tengo 5 productores y 2 consumidores en múltiples hilos. Básicamente, este programa agrega 100 elementos a la cola. El productor dejará de agregar cuando el tamaño de la cola sea 100. Me gustaría que el consumidor le notifique al productor cuando elimine todos los artículos de la cola para que el productor pueda comenzar a agregar nuevamente. Actualmente el productor esperará pero nunca será notificado por el consumidor.

Productor:

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();
            }
        }
    }
}

consumidor:

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();
            }
    }

  }
}

Clase principal

  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);
    }



   }
 }