This will probably be the simplest question on SO so first of all I apologize but I couldn't establish the answer so I had to ask it here.
Suppose you have a flowing list like this. I want to sum the dayId0 values, then dayId1 and print them on the upper layer in Room. For example, dayId0 will continue as food_kcal_sum=350 and dayId1 food_kcal_sum=45. How should I create a loop for this?
[
{
"dayId": 0,
"food_kcal": 270.0,
"id": 1
},
{
"dayId": 0,
"food_kcal": 60.0,
"id": 2
},
{
"dayId": 0,
"food_kcal": 20.0,
"id": 3
},
{
"dayId": 1,
"food_kcal": 15.0,
"id": 4
},
{
"dayId": 1,
"food_kcal": 30.0,
"id": 5
}
]
CodePudding user response:
I made an attempt using Gson.
public class DriverClass {
Map<Integer, Integer> mapValues = new HashMap<>();
public static void main(String[] args) {
Map<Integer, Integer> map = new DriverClass().sumValues();
map.entrySet().forEach(i -> System.out.println(i.getKey() " " i.getValue()));
}
private Map<Integer, Integer> sumValues() {
Gson gson = new Gson();
JsonArray jsonArray = gson.fromJson(myJson(), JsonArray.class);
for (int i = 0; i < jsonArray.size(); i ) {
JsonObject jsonObject = jsonArray.get(i).getAsJsonObject();
JsonElement jsonElementDayId = jsonObject.get("dayId");
JsonElement jsonElementFoodCal = jsonObject.get("food_kcal");
calculateValues(jsonElementDayId.getAsInt(), jsonElementFoodCal.getAsInt());
}
return mapValues;
}
private void calculateValues(int jsonElementDayId, int jsonElementFoodCal) {
if (mapValues.containsKey(jsonElementDayId)) {
mapValues.put(jsonElementDayId, mapValues.get(jsonElementDayId) jsonElementFoodCal);
} else {
mapValues.put(jsonElementDayId, jsonElementFoodCal);
}
}
public static String myJson() {
return """
[
{
"dayId": 0,
"food_kcal": 270.0,
"id": 1
},
{
"dayId": 0,
"food_kcal": 60.0,
"id": 2
},
{
"dayId": 0,
"food_kcal": 20.0,
"id": 3
},
{
"dayId": 1,
"food_kcal": 15.0,
"id": 4
},
{
"dayId": 1,
"food_kcal": 30.0,
"id": 5
}
]
""";
}
}
outputs:
0 350
1 45