Blackberry thread pool not working well

Question

I'm developing a thread pool in java for blackberry, this is the code I currently have:

public class ThreadPool {

    int maxWorkers = 15;
    Vector queue = new Vector();
    Thread[] workers;

    public ThreadPool(int maxThreads) {



        if (maxThreads <= maxWorkers)
            maxWorkers = maxThreads;

        workers = new Thread[maxThreads];


        for (int i = 0; i < maxThreads; i++) {

            // Crea un worker que ejecuta trabajos.
            workers[i] = new Thread(new Runnable() {

                public void run() {

                    Runnable r;

                    while (true) {

                        synchronized (queue) {

                            while (queue.size() == 0) {
                                try {
                                    queue.wait();
                                } catch (Exception e) {
                                    System.out.println("Error while waiting");
                                }
                            }

                            try {

                                r = (Runnable) queue.firstElement();
                                queue.removeElement(r);
                                r.run();
                                queue.notify();
                            } catch (Throwable e) {
                                System.out.println("nope!");
                            }
                        }
                    }
                }
            });


            workers[i].start();
        }
    }

    public void addWork(Runnable work) {

        synchronized (queue) {
            queue.addElement(work);
            queue.notify();
        }
    }
}

The problem is that if I queue 10 jobs, they will execute one after another, not in a concurrently way, for instance:

 for (int i=0; i<10; i++) {
        pool.addWork(new Runnable() {

                public void run() {

                    Random random = new Random();
                    int time = random.nextInt(5) * 1000;


                                System.out.println("I'm work " + i);

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

And I get:

I'm work 1
I'm work 2
I'm work 3
...

Answer 1

You are executing your job (i.e. r.run()) inside the queue synchronized statement, therefore, the queue lock isn't released until after each thread completes it's job. You should execute the job outside the synchronized statement. Try that.