public void addFooter(@NonNull View view){
  if (view == null) {
    throw new IllegalArgumentException("You can't have a null footer!");
  }
  mFooters.add(view);
}

public void addFooter ( @ NonNull View view ) { if ( view == null ) { throw new IllegalArgumentException ( "You can't have a null footer!" ) ; } mFooters . add ( view ) ; }
adds a footer view .
