String jsonStr = "{\"name\" : \"Abcd\", \"greeting\": \"Hello\", }"; //Sample Json String

Gson gson = new Gson(); // Creates new instance of Gson
JsonElement element = gson.fromJson (jsonStr, JsonElement.class); //Converts the json string to JsonElement without POJO 
JsonObject jsonObj = element.getAsJsonObject(); //Converting JsonElement to JsonObject

String name = jsonObj.get("name").getAsString(); //To fetch the values from json object
String greeting = jsonObj.get("greeting").getAsString();