public GcsUri resolve(String path) {
    Path relativePath = Paths.get(path);
    checkState(!relativePath.isAbsolute(), "path is absolute");
    String resolvedPath = _absolutePath.get().resolve(relativePath).toString();
    return createGcsUri(getBucketName(), resolvedPath);
  }
@Test
  public void testResolve() {
    GcsUri gcsUri = new GcsUri(URI.create("gs://bucket_name/dir"));
    GcsUri subDir = gcsUri.resolve("subdir/file");
    assertEquals(new GcsUri(URI.create("gs://bucket_name/dir/subdir/file")), subDir);
  }