@Override
  public void close() throws IOException {
    if (mUfsInStream.isPresent()) {
      mUfsInStream.get().close();
      mUfsInStream = Optional.empty();
    }
  }
@Test
  public void readWithNullUfsStream() {
    assertThrows(NullPointerException.class,
        () -> new UfsFileInStream(null, 0L).close());
  }