code: private void sort(List<ClassDoc> list) {
          List<ClassDoc> classes = new ArrayList<ClassDoc>();
          List<ClassDoc> interfaces = new ArrayList<ClassDoc>();
          for (int i = 0; i < list.size(); i++) {
              ClassDoc cd = list.get(i);
              if (cd.isClass()) {
                  classes.add(cd);
              } else {
                  interfaces.add(cd);
              }
          }
          list.clear();
          list.addAll(classes);
          list.addAll(interfaces);
      }
docs: Sort the given mixed list of classes and interfaces to a list of
  classes followed by interfaces traversed. Don't sort alphabetically.