@Override
  public SecureDirectoryStream<Path> newDirectoryStream(Path path, LinkOption... options)
      throws IOException {
    checkOpen();
    JimfsPath checkedPath = checkPath(path);

    // safe cast because a file system that supports SecureDirectoryStream always creates
    // SecureDirectoryStreams
    return (SecureDirectoryStream<Path>)
        view.newDirectoryStream(
            checkedPath,
            ALWAYS_TRUE_FILTER,
            Options.getLinkOptions(options),
            path().resolve(checkedPath));
  }
A stream filter that always returns true.
jimfs/src/main/java/com/google/common/jimfs/JimfsSecureDirectoryStream.java