CyclicBarrier3

CyclicBarrier3 is a concurrency utility that extends the functionality of the standard Java CyclicBarrier by allowing three parties to synchronize at a common barrier point. The original CyclicBarrier supports an arbitrary number of parties, but CyclicBarrier3 is specifically optimized for scenarios where exactly three threads must reach a synchronization point before any of them can proceed. This specialization can reduce overhead and simplify thread coordination logic in applications that routinely experience triadic synchronization patterns.

The core of CyclicBarrier3’s design mirrors that of java.util.concurrent.CyclicBarrier. It accepts an integer count (fixed at three), an optional Runnable barrier action that executes once all parties have arrived, and an optional timeout. Threads invoke await() to signal arrival and block until all three have called await. When the count reaches zero, the barrier action runs on one of the participating threads, and then the barrier is reset automatically for reuse in subsequent cycles. If the timeout elapses before all parties arrive, an InterruptedException is thrown, allowing the application to handle timing issues.

Typical usage involves three worker threads that perform independent phases of a computation and need to synchronize before advancing to the next phase, such as in a pipeline that processes data in three stages. In Java code, CyclicBarrier3 might look like:

public class CyclicBarrier3 {

private final CyclicBarrier barrier = new CyclicBarrier(3, () -> System.out.println("Phase complete"));

public void await() throws InterruptedException, BrokenBarrierException {

barrier.await();

}

}

Because the barrier is cyclic, it can be reused indefinitely, making it suitable for iterative algorithms. Compared to Semaphore or CountDownLatch, CyclicBarrier3 guarantees that all three parties proceed together and that no thread can advance prematurely. It is especially useful in simulation, rendering pipelines, or distributed systems where exactly three participants must coordinate frequent, symmetric steps.