public void invalidateTitleSortable(){
  for (  Movie movie : new ArrayList<>(movieList)) {
    movie.clearTitleSortable();
  }
}

public void invalidateTitleSortable ( ) { for ( Movie movie : new ArrayList < > ( movieList ) ) { movie . clearTitleSortable ( ) ; } }
invalidate the title sortable upon changes to the sortable prefixes
