* QPS=5 (5 tokens per second), if we ensure that a request isn't granted earlier than 200ms after
   * the last one, then we achieve the intended rate. If a request comes and the last request was
   * granted only 100ms ago, then we wait for another 100ms. At this rate, serving 15 fresh permits
   * (i.e. for an acquire(15) request) naturally takes 3 seconds.
   *

/**
 * Dispatches events to listeners, and provides ways for listeners to register themselves.
 *
 * <h2>Avoid EventBus</h2>
 *
 * <p><b>We recommend against using EventBus.</b> It was designed many years ago, and newer
 * libraries offer better ways to decouple components and react to events.
 *
 * <p>To decouple components, we recommend a dependency-injection framework. For Android code, most

 * of the code may not be readable by older versions of the code (e.g., a serialized Bloom filter
 * generated today may <i>not</i> be readable by a binary that was compiled 6 months ago).
 *
 * <p>As of Guava 23.0, this class is thread-safe and lock-free. It internally uses atomics and
 * compare-and-swap to ensure correctness when multiple threads are used to access it.
 *