RateLimiter.java

public class RateLimiter {

    private final double permitsPerSecond;

    private long nextAvailabilityNanos;

    public RateLimiter(final double permitsPerSecond) {
        this.permitsPerSecond = permitsPerSecond;
    }

    protected long nanoTime() {
        return System.nanoTime();
    }

    public long backoffNanos() {
        return Math.max(0, nextAvailabilityNanos - nanoTime());
    }

    public void take() {
        take(1);
    }

    public void take(double permits) {
        final long nowNanos = nanoTime();
        nextAvailabilityNanos = nowNanos
                + Math.max(0, nextAvailabilityNanos - nowNanos)
                + (long) (1000000000L * (permits / permitsPerSecond));
    }

}