What are the differences between CyclicBarrier and CountDownLatch?

CountDownLatch:

• Used for one or more threads to wait for the completion of other threads.
• Initialized with a counter that decreases when countDown() is called.
• Waiting threads are blocked by calling await().
• When the counter reaches zero, all waiting threads are released.
• Threads can call await() multiple times, but the counter does not reset.

CyclicBarrier:

• Used to synchronize a group of threads at a certain point ("barrier").
• Initialized with the number of threads that must reach the barrier.
• Threads block by calling await(), until all expected threads reach the barrier.
• Once all threads reach the barrier, they are released.
• The barrier is "cyclic" - it can be reused after all threads have passed through it.
• It can have an optional action performed by one of the threads after all threads reach the barrier but before they are released.

Comparison table:

Characteristic	CountDownLatch	CyclicBarrier
Purpose	One/multiple wait for others	Group of threads synchronize
State reset	No	Yes
Threads waiting	Those calling await()	All that must reach the barrier
Optional action	No	Yes