protected static String[] toStringArray( FilterType[] filterTypes ) {
    return Arrays.stream( filterTypes ).map( Enum::toString ).toArray( String[]::new );
  }
@Test
  public void toStringArray() {
    FilterType[] filterTypes = new FilterType[] { FilterType.ALL, FilterType.CSV, FilterType.TXT };
    String[] expectedFilterTypes =  new String[] { "ALL", "CSV", "TXT" };
    assertArrayEquals( expectedFilterTypes, SelectionAdapterOptions.toStringArray( filterTypes ) );
  }