public Builder addListenUrl(String url){
  if (UrlUtil.isUrl(url)) {
    if (mListenUrls == null) {
      mListenUrls=new HashSet<String>();
    }
    mListenUrls.add(url);
  }
  return this;
}

public Builder addListenUrl ( String url ) { if ( UrlUtil . isUrl ( url ) ) { if ( mListenUrls == null ) { mListenUrls = new HashSet < String > ( ) ; } mListenUrls . add ( url ) ; } return this ; }
add the url for listening
