code: private boolean add(Map<ClassDoc, SortedSet<ClassDoc>> map, ClassDoc superclass, ClassDoc cd) {
          SortedSet<ClassDoc> list = map.get(superclass);
          if (list == null) {
              list = new TreeSet<>(comparator);
              map.put(superclass, list);
          }
          if (list.contains(cd)) {
              return false;
          } else {
              list.add(cd);
          }
          return true;
      }
docs: Adjust the Class Tree. Add the class interface  in to it's super-class'
  or super-interface's sub-interface list.
  
  @param map the entire map.
  @param superclass java.lang.Object or the super-interface.
  @param cd sub-interface to be mapped.
  @returns boolean true if class added, false if class already processed.