private void initializeCssOnErrorSet(){
  if (cssOnErrorSet == null) {
    cssOnErrorSet=new ArrayList<>();
  }
  cssOnErrorSet.clear();
}

private void initializeCssOnErrorSet ( ) { if ( cssOnErrorSet == null ) { cssOnErrorSet = new ArrayList < > ( ) ; } cssOnErrorSet . clear ( ) ; }
this method initializes or re - initializes the set of stylesheets on error related with a css
