以下是使用gson时应该执行的步骤
1.获取单独在“results”中的json对象的键
1.将其作为具有键和值的json对象获取
1.收集JSON的条目集
1.创建一个迭代器，以便以后可以提取密钥
下面是执行相同工作的代码：

public static void main(String[] args) throws Exception {

        String json = "{\r\n" + 
                "   \"status\":true,\r\n" + 
                "   \"results\":{\r\n" + 
                "      \"type1\":{\r\n" + 
                "         \"id\":\"type1\"\r\n" + 
                "      },\r\n" + 
                "      \"type2\":{\r\n" + 
                "         \"id\":\"type2\"\r\n" + 
                "      }\r\n" + 
                "   }\r\n" + 
                "}";

        JsonParser parser = new JsonParser();
        JsonObject obj = parser.parse(json).getAsJsonObject();

        //get keys of the json objects which are inside "results" alone
        //get it as json object which has keys and values
        //collect the entry set our of the JSON
        //create an iterator so that later you can extract the keys
        Iterator<Entry<String, JsonElement>> iterator = obj.get("results")
                                                            .getAsJsonObject()
                                                            .entrySet()
                                                            .iterator();

        while(iterator.hasNext()) {
            //here you will get the keys like - type1 and type2
            System.out.println(iterator.next().getKey());
        }

    }

**代码编辑：**What @fluffy pointed完全有意义。进行了更改