CODEWITHSUNDEEP
javamultithreading
user1730789
user1730789

Reputation: 5177

Mutex and Semaphore in JAVA?

Is the Synchronized keyword in java depend on a Mutex or a Semaphore ? I read that both these terms are used interchangeably, but there is a difference ? Are there any built in Semaphore classes in java ?

Upvotes: 1

Views: 1684

Answers (3)

clinton
clinton

Reputation: 612

Semaphore has a fixed number of permits which can be acquired/released while running a block of code. So a fixed number of threads equal to number of permits can run a code block at the same time. Mutex/Lock is a specialized version of the Semaphore where the number of permits is 1. That is only a single thread is allowed to run a certain code block. This gives the thread 'ownership' of the code block. Only the owner can acquire and release the lock on the code block.

Upvotes: 0

Aubin
Aubin

Reputation: 14853

synchronized are implemented in term of Thread Monitor

java.util.concurrent.locks is a package which contains some useful lock relative classes like ReentrantLock

Upvotes: 0

Serge
Serge

Reputation: 6095

The main difference between a mutex and a semaphore is that the mutex may be released only by the process/thread that holds it in contrast to the semaphore that may be released by any process/thread. There is also one more difference but not as significant: there is a kind of semaphore that is called counting semaphore, i.e. a semaphore that may be initialized to allow several concurrent 'holders'.

The synchronized access in Java semantically should be implemented using mutex.

Upvotes: 1

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