[Java - Synchronization] Latches

1) Countdown Latch

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

A CountDownLatch is initialized with a given count. The await method is blocked until the current count reaches zero; we can reduce current count using the method, countDown().
The count cannot be reset. 

2) Cyclic Barrier

Similar to countdown latch, but the count can reset.


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