code: public static BundleFile newInstance(Resource res) {
  
  	try {
  	    BundleFile bf = new BundleFile(res);
  	    if (bf.isBundle()) return bf;
  	}
  	catch (Throwable t) {
  	    ExceptionUtil.rethrowIfNecessary(t);
  	}
  
  	return null;
      }
docs: only return a instance if the Resource is a valid bundle, otherwise it returns null
  
  @param res
  @return