code: protected void addClassList(Content contentTree) {
          List<String> classTableHeader = Arrays.asList(
                  resources.getText("doclet.Class"), resources.getText("doclet.Description"));
          for (String packageName : usingPackageToUsedClasses.keySet()) {
              PackageElement usingPackage = utils.elementUtils.getPackageElement(packageName);
              HtmlTree li = new HtmlTree(HtmlTag.LI);
              li.addStyle(HtmlStyle.blockList);
              if (usingPackage != null) {
                  li.addContent(getMarkerAnchor(utils.getPackageName(usingPackage)));
              }
              String tableSummary = configuration.getText("doclet.Use_Table_Summary",
                                                          configuration.getText("doclet.classes"));
              Content caption = getTableCaption(configuration.getContent(
                      "doclet.ClassUse_Classes.in.0.used.by.1",
                      getPackageLink(packageElement, utils.getPackageName(packageElement)),
                      getPackageLink(usingPackage, utils.getPackageName(usingPackage))));
              Content table = (configuration.isOutputHtml5())
                      ? HtmlTree.TABLE(HtmlStyle.useSummary, caption)
                      : HtmlTree.TABLE(HtmlStyle.useSummary, tableSummary, caption);
              table.addContent(getSummaryTableHeader(classTableHeader, "col"));
              Content tbody = new HtmlTree(HtmlTag.TBODY);
              boolean altColor = true;
              for (TypeElement te : usingPackageToUsedClasses.get(packageName)) {
                  HtmlTree tr = new HtmlTree(HtmlTag.TR);
                  tr.addStyle(altColor ? HtmlStyle.altColor : HtmlStyle.rowColor);
                  altColor = !altColor;
                  addClassRow(te, usingPackage, tr);
                  tbody.addContent(tr);
              }
              table.addContent(tbody);
              li.addContent(table);
              contentTree.addContent(li);
          }
      }
docs: Add the list of classes that use the given package.
  
  @param contentTree the content tree to which the class list will be added