SimpleRateLimiter

public class SimpleRateLimiter {
    private Semaphore semaphore;
    private int maxPermits;
    private TimeUnit timePeriod;
    private ScheduledExecutorService scheduler;

    public static SimpleRateLimiter create(int permits, TimeUnit timePeriod) {
        SimpleRateLimiter limiter = new SimpleRateLimiter(permits, timePeriod);
        limiter.schedulePermitReplenishment();
        return limiter;
    }

    private SimpleRateLimiter(int permits, TimeUnit timePeriod) {
        this.semaphore = new Semaphore(permits);
        this.maxPermits = permits;
        this.timePeriod = timePeriod;
    }

    public boolean tryAcquire() {
        return semaphore.tryAcquire();
    }

    public void stop() {
        scheduler.shutdownNow();
    }

    public void schedulePermitReplenishment() {
        scheduler = Executors.newScheduledThreadPool(1);
        scheduler.schedule(() -> {
            semaphore.release(maxPermits - semaphore.availablePermits());
        }, 1, timePeriod);

    }
}

should be :

scheduler.schedule(() -> {
            semaphore.release(maxPermits - semaphore.availablePermits());
        }, 0, 1, timePeriod);`

Building on @dbbogjoe
Should be :
```
scheduler.scheduleWithFixedDelay(() -> {
semaphore.release(maxPermits - semaphore.availablePermits());
}, 0, 1, timePeriod);

Yes, @namsor is right: scheduleWithFixedDelay or scheduleAtFixedRate should be used, otherwise the command will just be executed once. Apart from that: great tutorial, thanks!

Is there a sample unit test to test that class?

I don't have one easily available