private void scheduleRefresh(Set<String> toRefresh) {
    synchronized (myLock) {
      myRefreshQueue.addAll(toRefresh);
      if (myScheduledFuture == null) {
        myScheduledFuture = myExecutor.schedule(this::performRefresh, REFRESH_DELAY, TimeUnit.MILLISECONDS);
      }
    }
  }
private void scheduleRefresh(Set<String> toRefresh)