A synchronization aid that allows one or more fibers to wait until a set of operations being performed in other fibers completes.
A CountDownLatch
is initialized with a given count. The await
method
block until the current count reaches zero due to invocations of the
countDown
method, after which all waiting fibers are released and any
subsequent invocations of await
return immediately. This is a one-shot
phenomenon -- the count cannot be reset. If you need a version that resets
the count, consider using a CyclicBarrier.
A CountDownLatch
is a versatile synchronization tool and can be used for a
number of purposes. A CountDownLatch
initialized with a count of one serves
as a simple on/off latch, or gate: all fibers invoking await
wait at the
gate until it is opened by a fiber invoking countDown
. A CountDownLatch
initialized to N can be used to make one fiber wait until N fibers have
completed some action, or some action has been completed N times.
A useful property of a CountDownLatch
is that it doesn't require that
fibers calling countDown
wait for the count to reach zero before
proceeding, it simply prevents any fiber from proceeding past an await
until all fibers could pass.
- Companion:
- object