code: private boolean verify(String version, Long time) {
      if (versionToItem.containsKey(version)) {
        Path path = collectionCachePath.resolve(version);
        File file = path.toFile();
        if (file.exists() && file.canRead() && file.canWrite()) {
          if (time != null) {
            if (!file.setLastModified(time)) {
              log.debug("couldn't change filetime " + file.getAbsolutePath());
            } else {
              expirationVersion.put(version, time + (1000 * lifeTime));
            }
          }
          return true;
        } else {
          return false;
        }
      } else {
        return false;
      }
    }
docs: Verify.
  
  @param version the version
  @param time the time
  @return true, if successful