private Map<String,List<ProgramElementDoc>> pkgDivide(Map<String,? extends List<? extends ProgramElementDoc>> classMap) {
        Map<String,List<ProgramElementDoc>> map = new HashMap<String,List<ProgramElementDoc>>();
        List<? extends ProgramElementDoc> list= classMap.get(classdoc.qualifiedName());
        if (list != null) {
            Collections.sort(list);
            Iterator<? extends ProgramElementDoc> it = list.iterator();
            while (it.hasNext()) {
                ProgramElementDoc doc = it.next();
                PackageDoc pkg = doc.containingPackage();
                pkgSet.add(pkg);
                List<ProgramElementDoc> inPkg = map.get(pkg.name());
                if (inPkg == null) {
                    inPkg = new ArrayList<ProgramElementDoc>();
                    map.put(pkg.name(), inPkg);
                }
                inPkg.add(doc);
            }
        }
        return map;
    }