code: protected void addExtendsImplements(ClassDoc parent, ClassDoc cd,
              Content contentTree) {
          ClassDoc[] interfaces = cd.interfaces();
          if (interfaces.length > (cd.isInterface()? 1 : 0)) {
              Arrays.sort(interfaces);
              int counter = 0;
              for (int i = 0; i < interfaces.length; i++) {
                  if (parent != interfaces[i]) {
                      if (! (interfaces[i].isPublic() ||
                              Util.isLinkable(interfaces[i], configuration))) {
                          continue;
                      }
                      if (counter == 0) {
                          if (cd.isInterface()) {
                              contentTree.addContent(" (");
                              contentTree.addContent(getResource("doclet.also"));
                              contentTree.addContent(" extends ");
                          } else {
                              contentTree.addContent(" (implements ");
                          }
                      } else {
                          contentTree.addContent(", ");
                      }
                      addPreQualifiedClassLink(LinkInfoImpl.Kind.TREE,
                              interfaces[i], contentTree);
                      counter++;
                  }
              }
              if (counter > 0) {
                  contentTree.addContent(")");
              }
          }
      }
docs: Add information regarding the classes which this class extends or
  implements.
  
  @param parent the parent class of the class being documented
  @param cd the classdoc under consideration
  @param contentTree the content tree to which the information will be added