*/
    FAILED,
  }

  /**
   * A listener for the various state changes that a {@link Service} goes through in its lifecycle.
   *
   * <p>All methods are no-ops by default, implementors should override the ones they care about.
   *
   * @author Luke Sandberg
   * @since 15.0 (present as an interface in 13.0)
   */
  abstract class Listener {
    /**