public static void deleteDirectory(File directory) throws IOException {
    requireNonNull(directory, DIRECTORY_CAN_NOT_BE_NULL);
    deleteDirectoryImpl(directory.toPath());
  }
@Test
  public void deleteDirectory_throws_NPE_if_argument_is_null() throws IOException {
    assertThatThrownBy(() -> FileUtils.deleteDirectory((File) null))
      .isInstanceOf(NullPointerException.class)
      .hasMessage("Directory can not be null");
  }