I am preparing for interviews and just want to prepare some basic threading examples and structures so that I can use them during my white board coding if I have to.
I was reading about CyclicBarrier and was just trying my hands at it, so I wrote a very simple code:
import java.util.concurrent.CyclicBarrier;
public class Threads
{
/**
* @param args
*/
public static void main(String[] args)
{
// ******************************************************************
// Using CyclicBarrier to make all threads wait at a point until all
// threads reach there
// ******************************************************************
barrier = new CyclicBarrier(N);
for (int i = 0; i < N; ++i)
{
new Thread(new CyclicBarrierWorker()).start();
}
// ******************************************************************
}
static class CyclicBarrierWorker implements Runnable
{
public void run()
{
try
{
long id = Thread.currentThread().getId();
System.out.println("I am thread " + id + " and I am waiting for my friends to arrive");
// Do Something in the Thread
Thread.sleep(1000*(int)(4*Math.random()*10));
// Now Wait till all the thread reaches this point
barrier.await();
}
catch (Exception e)
{
e.printStackTrace();
}
//Now do whatever else after all threads are released
long id1 = Thread.currentThread().getId();
System.out.println("Thread:"+id1+" We all got released ..hurray!!");
System.out.println("We all got released ..hurray!!");
}
}
final static int N = 4;
static CyclicBarrier barrier = null;
}
You can copy paste it as is and run in your compiler.
What I want to verify is that indeed all threads wait at this point in code:
barrier.await();
I put some wait and was hoping that I would see 4 statements appear one after other in a sequential fashion on the console, followed by 'outburst' of "released..hurray" statement. But I am seeing outburst of all the statements together no matter what I select as the sleep.
Am I missing something here ?
Thanks P.S: Is there an online editor like http://codepad.org/F01xIhLl where I can just put Java code and hit a button to run a throw away code ? . I found some which require some configuration before I can run any code.
The code looks fine, but it might be more enlightening to write to System.out before the sleep. Consider this in run():
long id = Thread.currentThread().getId();
System.out.println("I am thread " + id + " and I am waiting for my friends to arrive");
// Do Something in the Thread
Thread.sleep(1000*8);
On my machine, I still see a burst, but it is clear that the threads are blocked on the barrier.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With