Executor Service with Blocking Queue

I did not find a single working implementation of using an Executor Service with a Blocking Queue. So , I have come with with a working sample. Thoughts?

import java.util.Map;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;

class Producer implements Runnable {

    protected BlockingQueue queue = null;

    public Producer(BlockingQueue queue) {
        this.queue = queue;
    }

    public void run() {
        try {

            for (int i = 0; i < 10000; i++) {
                queue.put(i);
                // System.out.println("Producer ID "+Thread.currentThread().getId()+" is adding task : "+i);
            }
            // poison pill
            // System.out.println("Poison number added! "+Thread.currentThread().getId());
            queue.put(-1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

class Consumer implements Runnable {

    protected BlockingQueue queue = null;
    ConcurrentHashMap<Integer, Integer> hashmap;

    public Consumer(BlockingQueue queue,
            ConcurrentHashMap<Integer, Integer> hashmap) {
        this.queue = queue;
        this.hashmap = hashmap;
    }

    public void run() {
        try {

            while (ExecutorTest.isRunning) {
                Integer i = (Integer) queue.take();
                System.out.println("Consumer " + Thread.currentThread().getId()
                        + ": taking Task : " + i);
                if (i == -1) {
                    queue.put(i);
                    ExecutorTest.isRunning = false;
                    // System.out.println("Setting isRunning to false :  "+Thread.currentThread().getId());
                    break;
                }
                hashmap.put(i, i);
            }

        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

public class ExecutorTest {

    static BlockingQueue<Integer> queue = new LinkedBlockingQueue<Integer>();
    static ConcurrentHashMap<Integer, Integer> hashmap = new ConcurrentHashMap<Integer, Integer>();
    static volatile boolean isRunning = true;

    public static void main(String[] args) {
        Producer producer = new Producer(queue);
        Consumer consumer = new Consumer(queue, hashmap);

        new Thread(producer).start();
        ExecutorService executorService = Executors.newFixedThreadPool(4);

        executorService.execute(consumer);
        executorService.execute(consumer);
        executorService.execute(consumer);
        executorService.execute(consumer);

        // wait for the threads to finish
        while (isRunning) {
        };

        executorService.shutdown();
        System.out.println("SHUT DOWN THREAD POOL");

        try {
            executorService.awaitTermination(10, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("HASHMAP SIZE : " + hashmap.size());
    }

    public static void printHashMap() {
        for (Map.Entry<Integer, Integer> map : hashmap.entrySet()) {
            System.out.println("Entry " + map.getKey() + ":" + map.getValue());
        }
    }

}