How to use

org.apache.wicket.markup.html.resources.StyleSheetReference

constructor

/**
 * Can be overridden by clients for custom style sheet
 * 
 * @return the style sheet reference
 */
protected StyleSheetReference getStyleSheet()
{
  return new StyleSheetReference("paletteCSS", getClass(), "palette.css");
}

 public NavigationComponent( @NotNull @NonNls String id, @NotNull final LinksDataView dataView, @Nullable ResourceReference styleSheetReference ) {
  super( id );

  if ( styleSheetReference == null ) {
   add( new EmptyPanel( WicketConstants.ID_STYLE_SHEET ) );
  } else {
   add( new StyleSheetReference( WicketConstants.ID_STYLE_SHEET, styleSheetReference ) );
  }

  WebMarkupContainer container = new WebMarkupContainer( ID_NAVIGATION_UL );
  add( container );
  container.add( dataView );
 }
}

 public NavigationComponent( @Nonnull @NonNls String id, @Nonnull final LinksDataView<?> dataView, @Nullable ResourceReference styleSheetReference ) {
  super( id );

  if ( styleSheetReference == null ) {
   add( new EmptyPanel( WicketConstants.ID_STYLE_SHEET ) );
  } else {
   add( new StyleSheetReference( WicketConstants.ID_STYLE_SHEET, styleSheetReference ) );
  }

  WebMarkupContainer container = new WebMarkupContainer( NAVIGATION_UL );
  add( container );
  container.add( dataView );

  //Adds the big reference
  container.add( new AbstractBehavior() {
   @Override
   public void onComponentTag( @Nonnull Component component, @Nonnull ComponentTag tag ) {
    if ( dataView.getRowCount() > 6 ) {
     tag.put( "id", "big" );
    } else {
     tag.put( "id", "small" );
    }
   }
  } );
 }
}