code: public static GTFSFeed fromFile(String file, String feedId) {
          GTFSFeed feed = new GTFSFeed();
          ZipFile zip;
          try {
              zip = new ZipFile(file);
              if (feedId == null) {
                  feed.loadFromFile(zip);
              }
              else {
                  feed.loadFromFile(zip, feedId);
              }
              zip.close();
              return feed;
          } catch (Exception e) {
              LOG.error("Error loading GTFS: {}", e.getMessage());
              throw new RuntimeException(e);
          }
      }
docs: Static factory method returning a new instance of GTFSFeed containing the contents of
  the GTFS file at the supplied filesystem path. Forces the feedId to the
  supplied value if the parameter is non-null.