code: protected void addClassListing(HtmlTree contentTree) {
          Configuration config = configuration;
          if (utils.isSpecified(packageElement)) {
              addClassKindListing(utils.getInterfaces(packageElement),
                  contents.interfaces, contentTree);
              addClassKindListing(utils.getOrdinaryClasses(packageElement),
                  contents.classes, contentTree);
              addClassKindListing(utils.getEnums(packageElement),
                  contents.enums, contentTree);
              addClassKindListing(utils.getExceptions(packageElement),
                  contents.exceptions, contentTree);
              addClassKindListing(utils.getErrors(packageElement),
                  contents.errors, contentTree);
              addClassKindListing(utils.getAnnotationTypes(packageElement),
                  contents.annotationTypes, contentTree);
          } else {
              addClassKindListing(config.typeElementCatalog.interfaces(packageElement),
                  contents.interfaces, contentTree);
              addClassKindListing(config.typeElementCatalog.ordinaryClasses(packageElement),
                  contents.classes, contentTree);
              addClassKindListing(config.typeElementCatalog.enums(packageElement),
                  contents.enums, contentTree);
              addClassKindListing(config.typeElementCatalog.exceptions(packageElement),
                  contents.exceptions, contentTree);
              addClassKindListing(config.typeElementCatalog.errors(packageElement),
                  contents.errors, contentTree);
              addClassKindListing(config.typeElementCatalog.annotationTypes(packageElement),
                  contents.annotationTypes, contentTree);
          }
      }
docs: Add class listing for all the classes in this package. Divide class
  listing as per the class kind and generate separate listing for
  Classes, Interfaces, Exceptions and Errors.
  
  @param contentTree the content tree to which the listing will be added