java.util.concurrent · java.base · since Java 1.5

Semaphore

declaration

public class Semaphore implements Serializable

A permit counter bounding concurrent access: acquire/release around any scarce resource. With virtual threads, the replacement for pool-size-as-limit.

Key methods

`Semaphore(int permits, boolean fair)`	Fairness prevents starvation at some throughput cost.
`void acquire() / void release()`	Take and return a permit (release in finally!).
`boolean tryAcquire(long timeout, TimeUnit)`	Bounded wait — the load-shedding form.