String与StringBuffer传参的区别（1）

  private void getValue(StringBuffer denIszero, StringBuffer denIsNull){
       
        Connection conn = null;
       
        Statement stmt = null;
       
        ResultSet rset = null;
       
        conn = getConnection();
       
        Map<String, StringBuffer> map = new HashMap<String, StringBuffer>();
        try
        {
            stmt = conn.createStatement();
           
            StringBuffer str = new StringBuffer();
           
            str.append("select t.id,t.value from t_sys_parameter t where t.id in ('");
            str.append(Constants.DEN_ZERO_DISPLAY);
            str.append("' , '");
            str.append(Constants.DEN_ZERO_IS_USE);
            str.append("' , '");
            str.append(Constants.DEN_NUM_NULL_DISPLAY);
            str.append("' , '");
            str.append(Constants.DEN_NUM_NULL_IS_USE);
            str.append("')");
           
            //从数据库中获取ID和VALUE
            rset = stmt.executeQuery(str.toString());
           
            //把从数据库中获取的结果集循环放在MAP里，ID字段为键，value字段为值
            while(rset.next())
            {
               map.put(rset.getString("id"), new StringBuffer(rset.getString("value")));
            }
           
            //当分母为零时，判断它是否被启用，如果启用了，返回结果为1，否则为0
            String zeroValue = map.get(Constants.DEN_ZERO_IS_USE).toString();
            //如果返回为0，那么特殊标记为空
            if(Constants.DEN_ZERO_IN_USE.equals(zeroValue))
            {
                denIszero = null;
            }
           
            else
            {
                //如果返回1，特殊标记为从数据库中取得的值
               denIszero.append(map.get(Constants.DEN_ZERO_DISPLAY));
            }
           
           //当分子为空或分母为空时，判断它是否被启用，如果启用了，返回结果为1，否则为0
            String nullValue = map.get(Constants.DEN_NUM_NULL_IS_USE).toString();
            //如果返回为0，那么特殊标记为空
            if(Constants.DEN_NULL_IN_USE.equals(nullValue))
            {
                denIsNull = null;
            }
           
            else
            {
                //如果返回1，特殊标记为从数据库中取得的值
                denIsNull.append(map.get(Constants.DEN_NUM_NULL_DISPLAY));
            }
               
        }
        catch (SQLException e)
        {
            log.exceptionLog("SQLBuilderDAO.getCount()", e);
        }
    }