protected synchronized void ensurePrefetchAmount(){
  if (mPrefetchedAdList.size() < PREFETCHED_ADS_SIZE && (mFetchFailCount < MAX_FETCH_ATTEMPT)) {
    fetchAd();
  }
}

protected synchronized void ensurePrefetchAmount ( ) { if ( mPrefetchedAdList . size ( ) < PREFETCHED_ADS_SIZE && ( mFetchFailCount < MAX_FETCH_ATTEMPT ) ) { fetchAd ( ) ; } }
ensures that the necessary amount of prefetched native ads are available .
