What is the usage of a cyclic barrier?

CyclicBarrier is a synchronization aid that allows a group of threads to wait for each other until all threads reach a certain barrier state before proceeding together. It can be used in scenarios where multiple threads are calculating data and need to merge the results at the end.

The CyclicBarrier is like a counter that is initialized with a specific value in its constructor. Each thread arriving at the barrier will decrement the counter by calling the await() method, until all threads have arrived and the counter reaches zero. At this point, all threads are released simultaneously and the barrier is reset for future use.

The main methods of CyclicBarrier include:

1. Wait on the barrier until all threads have arrived. Each thread calling this method will result in the counter decreasing by 1. When the counter reaches 0, all threads are released simultaneously.
2. Wait for a specified amount of time, if some threads have not reached the barrier before the specified time, then throw a TimeoutException.

The steps for using CyclicBarrier are as follows:

1. Create a CyclicBarrier instance, specifying the initial value of the counter and the action to be performed upon reaching the barrier.
2. In each thread, the await() method is called to wait for other threads to reach the barrier.
3. When all threads have reached the barrier, execute the specified action.
4. To reuse CyclicBarrier, you can achieve it by creating a new instance of it.