Grouping same date JSON data together Using java

Question

I have created one json Object Using java and it's values are given below

{
  "result":[
    {"ID":7252,"Age":52,"Date":"2015-11-25","DAY":"Wednesday","Gender":"M"},
    {"ID":7252,"Age":52,"Date":"2015-12-05","DAY":"Saturday","Gender":"M"},
    ....
  ],
  "status":"ok"
}

I need to group data as per date,required format is given below

{
  "result":[
    {"2015-11-25":[
      {"ID":7252,"Age":52,"Date":"2015-11-25","DAY":"Wednesday","Gender":"F"},
      {"ID":7252,"Age":52,"Date":"2015-11-25","DAY":"Wednesday","Gender":"M"}
    ]},
    {"2015-10-25":[
      {"ID":7252,"Age":52,"Date":"2015-10-25","DAY":"Tuesday","Gender":"F"},
      {"ID":7252,"Age":52,"Date":"2015-10-25","DAY":"Tuesday","Gender":"M"}
    ]},
  ],
  "status":"ok"
}

Basically i need group all same date data together inside JSON with date as key How can i achieve this JSON format using java

Answer 1

What kind of JSON mapper do you use? Jackson, GSON, ...?

And please provide some code. So we can see what you're doing.

---

If you created the JSON object using Java, you should have a Java Object structure, right?

Something like this:

class Data {
  int id;
  int age;
  LocalDate date;
  ...
}

And somewhere an Array / List of your data:

List<Data> result = new ArrayList<>();
result.add(data1);
result.add(data2);
result.add(data3);

Then you can use Java8 Stream API to group your data:

Map<LocalDate, Data> grouped = result
    .stream()
    .collect(
        Collectors.groupingBy(Data::getDate)
    );

The result will be a Map . Your result should be a List .

So you should be able to simply iterate over the Map and insert it into a new List .