How to make sure two threads printing even odd numbers maintain even first then odd order for this implementation?

Question

I have created two runnable jobs: PrintEvenNumbersJob and PrintOddNumbersJob and spawned two threads to execute these jobs. This seems to work perfectly fine! But I smell so

Answer 1

I tried and tested this code. It works using Semaphore

public class TestSemaphore
{

    public static void main(String[] args)
        throws Exception
    {
        AtomicInteger count = new AtomicInteger();
        Semaphore s = new Semaphore(1, true);
        Semaphore t = new Semaphore(1, true);

        OddNumberThread oThread = new OddNumberThread(count, s, t);
        EvenNumberThread eThread = new EvenNumberThread(count, s, t);

        eThread.start();
        oThread.start();
    }

    static class EvenNumberThread
        extends Thread
    {
        private AtomicInteger count;

        private Semaphore s, t;

        public EvenNumberThread(AtomicInteger pCount, Semaphore pS, Semaphore pT)
        {
            super("Even");
            count = pCount;
            s = pS;
            t = pT;
        }

        @Override
        public void run()
        {
            // Make this thread wait until even thread starts, Order will be incorrect if removed these lines.
            s.acquireUninterruptibly();
            while (count.intValue() <= 10)
            {
                try
                {
                    // Double checking to make it work
                    s.acquireUninterruptibly();

                    System.out.println(getName() + " " + count.getAndIncrement());
                }
                finally
                {
                    t.release();
                }
            }
        }
    }

    static class OddNumberThread
        extends Thread
    {
        private AtomicInteger count;

        private Semaphore s, t;

        public OddNumberThread(AtomicInteger pCount, Semaphore pS, Semaphore pT)
        {
            super("Odd");
            count = pCount;
            s = pS;
            t = pT;
        }

        @Override
        public void run()
        {
            // Start this thread first and start printing, Order will be incorrect if removed these lines.
            t.acquireUninterruptibly();
            s.release();

            while (count.intValue() <= 10)
            {
                try
                {
                    t.acquireUninterruptibly();

                    System.out.println(getName() + " " + count.getAndIncrement());
                }
                finally
                {
                    s.release();
                }
            }
        }
    }
}