@Override public int compare(Hymn a, Hymn b) { return (int) (a.getId() - b.getId()); }
@Override public int compare(Hymn a, Hymn b) { return a.getAuthor().compareTo(b.getAuthor()); }
@Override public int compare(Hymn a, Hymn b) { return a.getTitle().compareTo(b.getTitle()); }