What is difference between CyclicBarriar and CountdownLatch in Java ?

The main difference between CyclicBarrier and CountDownLatch is that CyclicBarrier is reusable and CountDownLatch is not. You can reuse CyclicBarrier by calling reset() method which resets the barrier to its initial state.

CountDownLatch is good for one time event like application/module start-up time and CyclicBarrier can be used to in case of recurrent event e.g. concurrently (re-)calculating each time when the input data changed.