List中取出相同属性值

需求：将List对象中相同的ShippingRuleName为key，所对应的所有id为val。

如上，处理成{"500": 2,"344344": 12,"DWD": "19,20,21,22","5件包邮": "3,4","test1111111": "23,24"}

List<BasicTemplate> basicTemplates = Service.queryTemplateGroupByName(param);
Map<String, Object> map = new HashMap<>();
 for (BasicTemplate order : basicTemplates) {
     String shippingRuleName = order.getShippingRuleName();//rulename
     Integer id = order.getId();// id
     // 如果map中没有当前的shippingRuleName
     if (!map.containsKey(shippingRuleName)) {
         // 将shippingRuleName和id添加进map中
         map.put(shippingRuleName, id);
     } else {
         // 取出shippingRuleName对应的id值
         Object o = map.get(shippingRuleName);
         StringBuffer sb2 = new StringBuffer();
         // 在之前的id后添加新的id，并以逗号隔开
         sb2.append(o).append(",").append(id);
         // 将拼接后的新id和之前shippingRuleName重新放入map中
         map.put(shippingRuleName, sb2.toString());
     }
 }