When Semaphore Is Used?

The correct use of a semaphore is for signaling from one task to another. A mutex is meant to be taken and released, always in that order, by each task that uses the shared resource it protects. By contrast, tasks that use semaphores either signal or wait—not both.

When should you use semaphore?

General semaphores are used for "counting" tasks such as creating a critical region that allows a specified number of threads to enter. For example, if you want at most four threads to be able to enter a section, you could protect it with a semaphore and initialize that semaphore to four.

Why semaphore is used in Java?

A semaphore controls access to a shared resource through the use of a counter. If the counter is greater than zero, then access is allowed. If it is zero, then access is denied.