public void addCssClass(String cssClass) {
   if (this.isHeaderColumn) {
     StringBuilder cssClassSb =
         DatatableOptions.CSSCLASS.valueFrom(this.columnConfiguration.getOptions());
     if (cssClassSb != null && cssClassSb.length() != 0) {
       DatatableOptions.CSSCLASS.appendIn(this.columnConfiguration.getOptions(), CLASS_SEPARATOR);
     }
     DatatableOptions.CSSCLASS.appendIn(this.columnConfiguration.getOptions(), cssClass);
   } else {
     if (this.cssClass == null) {
       this.cssClass = new StringBuilder();
     } else {
       this.cssClass.append(CLASS_SEPARATOR);
     }
     this.cssClass.append(cssClass);
   }
 }