}
  }

  /** Runnable which registers a StringCatcher on an event bus and adds it to a list. */
  private static class Registrator implements Runnable {
    private final EventBus bus;
    private final List<StringCatcher> catchers;

    Registrator(EventBus bus, List<StringCatcher> catchers) {
      this.bus = bus;
      this.catchers = catchers;
    }

    @Override