code: private void addThemeLinks(PageParameters parameters){
          if (parameters.getAllNamed().size() < 2) {
              add(new UpdateThemeLink("defaultTheme", "chart"));
              add(new UpdateThemeLink("grid", "chart"));
              add(new UpdateThemeLink("skies", "chart"));
              add(new UpdateThemeLink("gray", "chart"));
              add(new UpdateThemeLink("darkblue", "chart"));
          } else {
              String chartString = parameters.getAllNamed().get(1).getValue();
              add(new UpdateThemeLink("defaultTheme", chartString));
              add(new UpdateThemeLink("grid", chartString));
              add(new UpdateThemeLink("skies", chartString));
              add(new UpdateThemeLink("gray", chartString));
              add(new UpdateThemeLink("darkblue", chartString));
          }
      }
docs: Adds links to the different themes
  @param parameters the page parameters from the page URI