Java CyclicBarrier

A synchronization aid that allows a set of threads to all wait for each other to reach a common barrier point. CyclicBarriers are useful in programs involving a fixed sized party of threads that must occasionally wait for each other. The barrier is called cyclic because it can be re-used after the waiting threads are released.

A CyclicBarrier supports an optional Runnable command that is run once per barrier point, after the last thread in the party arrives, but before any threads are released. This barrier action is useful for updating shared-state before any of the parties continue.

more information could be found at CyclicBarrier in Oracle

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Java CountDownLatch

What is CountDownLatch?

A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes, i.e., a kind of synchronization tool that allows one Thread  to wait for one or more Threads before it starts processing.

How does CountDownLatch work?

A CountDownLatch is initialized with a given count. The await methods block until the current count reaches zero due to invocations of the countDown() method, after which all waiting threads 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.

more information could be found at CountDownLatch in Oracle Document Continue reading “Java CountDownLatch”

Callable and Future in Java

public interface Callable<V>

A task that returns a result and may throw an exception. Implementors define a single method with no arguments called call.

The Callable interface is similar to Runnable, in that both are designed for classes whose instances are potentially executed by another thread. A Runnable, however, does not return a result and cannot throw a checked exception.

The Executors class contains utility methods to convert from other common forms to Callable classes. Continue reading “Callable and Future in Java”