Synchronizing three steps in three different threads?

Question

In my main programme, i start three threads as described below

Thread 1:- having steps 1A and 1B

Thread 2:- having steps 2A and 2B

Thread 3:- having steps 3A and 3B

I want Thread 1, 2 and 3 proceed for their next step only when all of them complete their first step.

For example:- Thread 2 and Thread 3 have completed their first steps i.e 2A and 3A respectively but Thread1 did not complete step 1A. So thread 2 and 3 will wait till thread 1 complete step 1A

I know i can handle it with simple static counter and only proceed once counter value is 3. But i am sure there must be something off the shelve available in thread/java.util.concurrent package?

use the codes under synchronize block for reference: http://tutorials.jenkov.com/java-concurrency/synchronized.html — Rahul, Nov 18 '13 at 02:02

brettw · Accepted Answer · 2013-11-18T02:22:02.590

Use a java.util.concurrent.CyclicBarrier. For example, create a CyclicBarrier with a count of 3:

CyclicBarrier cb = new CyclicBarrier(3);
new Thread(new Thread1(cb)).start();
new Thread(new Thread2(cb)).start();
new Thread(new Thread3(cb)).start();

class Thread1 implements Runnable() {
   private CyclicBarrier barrier;
   public Thread1(CyclicBarrier cb) {
      barrier = cb;
   }

   public void run() {
       // execute 1A
       barrier.await();
       // execute 1B
}

class Thread2 implements Runnable() {
   private CyclicBarrier barrier;
   public Thread2(CyclicBarrier cb) {
      barrier = cb;
   }

   public void run() {
       // execute 2A
       barrier.await();
       // execute 2B
}

// repeat for Thread3

Each thread will execute until it reach the await() call, then it will stop until all 3 threads have reached that rendezvous point. When the third thread reaches that point (whichever one it is), the two that were waiting will proceed.

Synchronizing three steps in three different threads?

1 Answers1