layout	pattern
title	Semaphore
folder	semaphore
permalink	/patterns/semaphore/
pumlid	HSV14SCm20J0Lk82BFxf1ikCfOn06ZZizfDVVhjRjphobFJnQi2ADv7pKwwEbaU6U9q6CPGwbVh8Xy5E7xvvFoNwPVjYGDo2bEC72b5URRgGeFvNqhMirF45
categories	Concurrency
tags	Java Difficulty-Intermediate

Also known as

Counting Semaphore

Intent

Create a lock which mediates access to a pool of resources. Only a limited number of threads, specified at the creation of the semaphore, can access the resources at any given time. A semaphore which only allows one concurrent access to a resource is called a binary semaphore.

Applicability

Use a Semaphore when

• you have a pool of resources to allocate to different threads
• concurrent access to a resource could lead to a race condition

Credits

• [Semaphore(programming)] (http://en.wikipedia.org/wiki/Semaphore_(programming))
• [Semaphores] (http://tutorials.jenkov.com/java-concurrency/semaphores.html)