用java代码实现构造目录树

public String directory(String author)
    {
        StringBuffer treeHtml = new StringBuffer();
        // 得到所有的目录词（包含全部字段）
        List<Tutorial> words = bdExpandService.getAllWords(author);
        for (int i = 0; i < words.size(); i++)
        {
            Tutorial wordMap = words.get(i);
            // System.out.println(wordMap);
            if (wordMap.getPid() == 0)
            {
                treeHtml.append("<dl>");
                // 得到根目录的id，根据这个id找到这个的所有子目录
                appendTree(words, wordMap, treeHtml);
                treeHtml.append("</dl>");
            }
        }
        words.clear();
        return treeHtml.toString();
    }

    /**
     * 
     * 构造目录树 <功能详细描述>
     * 
     * @param tutorials
     * @param tutorial
     * @param treeHtml
     * @see [类、类#方法、类#成员]
     */
    private void appendTree(List<Tutorial> words, Tutorial wordMap, StringBuffer treeHtml)
    {
        int tid = wordMap.getTid();
        // 得到根目录的id，根据这个id找到这个的所有子目录
        Map<String, Object> map = childTreeHtml(words, tid);
        String nodeHtml = map.get("treeHtml").toString();
        boolean hasChild = Boolean.valueOf(map.get("hasChild").toString());
        if (hasChild)
        {
            treeHtml.append("<dt class=‘node-close‘ onclick=‘showTree(").append(tid).append(")‘");
            treeHtml.append("id=‘tree_dt").append(tid).append("‘>");
            treeHtml.append(wordMap.getKeyWord()).append("</dt>");
            treeHtml.append(nodeHtml);
        } else
        {
            treeHtml.append("<dt>");
            treeHtml.append(wordMap.getKeyWord()).append("</dt>");
        }
    }

    /**
     * 
     * 得到子目录，构造目录树 <功能详细描述>
     * 
     * @param tutorials
     * @param tid
     * @return
     * @see [类、类#方法、类#成员]
     */
    private Map<String, Object> childTreeHtml(List<Tutorial> words, int tid)
    {
        Map<String, Object> map = new HashMap<String, Object>();
        StringBuffer treeHtml = new StringBuffer();
        boolean hasChild = false;
        for (int i = 0; i < words.size(); i++)
        {
            Tutorial wordMap = words.get(i);
            int pid = wordMap.getPid();
            if (pid == tid)
            {
                hasChild = true;
                treeHtml.append("<dd name=‘tree_dd").append(pid).append("‘");
                treeHtml.append("style=‘display: none;‘>").append("<dl>");
                appendTree(words, wordMap, treeHtml);
                treeHtml.append("</dl></dd>");
            }
        }
        map.put("treeHtml", treeHtml);
        map.put("hasChild", hasChild);
        return map;
    }