Java concurrency: Countdown latch vs Cyclic barrier

Question

I was reading through the java.util.concurrent API, and found that

• CountDownLatch: A synchronization aid that allows one or more threads to wait

Answer 1

I think that the JavaDoc has explained the differences explicitly. Most people know that CountDownLatch can not be reset, however, CyclicBarrier can. But this is not the only difference, or the CyclicBarrier could be renamed to ResetbleCountDownLatch. We should tell the differences from the perspective of their goals, which are described in JavaDoc

CountDownLatch: A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes.

CyclicBarrier: A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point.

In countDownLatch, there is one or more threads, that are waiting for a set of other threads to complete. In this situation, there are two types of threads, one type is waiting, another type is doing something, after finishes their tasks, they could be waiting or just terminated.

In CyclicBarrier, there are only one type of threads, they are waiting for each other, they are equal.