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I am getting following response from an API 

String response={"balance":1000,
  "lastliability":2000,"profitarray":[[1,2,3],[67,88,99]],"previous":[99,88]}

I am trying to convert profitarray to ArrayList in Java like

    JSONObject res=new JSONObject(response);
    ArrayList<ArrayList<Integer>> temp=res.getString("profitarray")//something like this
ArrayList<Integer>yy=res.getString("previous");

Obviously, the outputs of res.getstring will be String and I want to convert them to ArrayList, any idea how to do it?

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5
  • 1
    Which JSON library are you using and doesn't it already have a way to return Lists/Arrays? Commented Nov 24, 2018 at 9:05
  • Are you asking how to get profitarray":[[1,2,3],[67,88,99]] from the response ? How to get [[1,2,3],[67,88,99]] from the response ? or how to convert this [[1,2,3],[67,88,99]] from a String to arraylist of Integers ? Commented Nov 24, 2018 at 9:05
  • @c0der i amalready getting them from response ,I want to convert them to respective arraylist so as to save them in database Commented Nov 24, 2018 at 9:06
  • @vlaz JSon simple Commented Nov 24, 2018 at 9:06
  • I want to convert the string response in arraylist ,the response is stringified array right. Commented Nov 24, 2018 at 9:11

3 Answers 3

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1

Could be a complex way to do it, but since you wanted an ArrayList>, here we are

public static void main(String[] args) {
    String response = "{\"balance\":1000,\n" +
            "  \"lastliability\":2000,\"profitarray\":[[1,2,3],[67,88,99]],\"previous\":[99,88]}";
    JSONObject res=new JSONObject(response);
    JSONArray array = res.getJSONArray("profitarray");
    ArrayList<JSONArray> profitList = new ArrayList<>();
    for (int i = 0; i < array.length(); i++){
        profitList.add(array.getJSONArray(i));
    }
    ArrayList<ArrayList<Integer>> finalList = new ArrayList<>();
    ArrayList<Integer> list1 = new ArrayList<>();
    for (int i = 0; i < profitList.size(); i++){
        JSONArray array1 = profitList.get(i);
        list1 = new ArrayList<>();
        for (int j = 0; j < array1.length(); j++){
            list1.add(array1.getInt(j));
        }
        finalList.add(list1);
    }
}

The ArrayList finalList contains the final output.

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Comments

0

The key thing is to create a Java class that model your response. See this example using Google Gson.

Response class:

import java.util.ArrayList;

public class Response {
//    int balance;
//    int lastLiability;
//    ArrayList<Integer> previous;
    ArrayList<ArrayList<Integer>> profitarray;
}

Gson example:

import com.google.gson.Gson;

public class GsonExample {
    public static void main(String[] args) {
        String json = "{\"balance\":1000,\"lastliability\":2000,\"profitarray\":[[1,2,3],[67,88,99]],\"previous\":[99,88]}";

        Response response = new Gson().fromJson(json, Response.class);
        System.out.println(response.profitarray);
    }
}

I guess that you should add accessors, equals/hashCode and all that noise — but you get the idea.

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Comments

0

You can use JsonArray to extract an array out of a JSON response. Later on, you can use Collections API to convert that array into an ArrayList.

    JsonObject res = new JsonObject(response);
    JsonArray array1 = res.getJsonArray("profitarray");
    JsonArray array2 = res.getJsonArray("previous");

    ArrayList<JsonObject> arrayList1 = new ArrayList(array1.length());
    ArrayList<JsonObject> arrayList2 = new ArrayList(array2.length());

    for(int i=0;i < array1.length();i++){
    arrayList1.add(array1.getJsonObject(i));
}
    for(int j=0;j < array2.length();j++){
    arrayList2.add(array2.getJsonObject(j));
}
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4 Comments

Is there a documentation for that? All I can find is this but it seems like the API is different - it's using JsonObject instead of JSONObject (different capitalisation). This is version 3, so perhaps it changed - I find some references to code using JSONObject but it seems to be for an earlier version some version 1 project points at a dead documentation source
Thanks for the observation. I have modified my answer for the same. By the by I had referred this: [oracle.com/technetwork/articles/java/json-1973242.html]
It dint work,I need ArrayList<ArrayList<Integer>> :(
array1 would not have worked but array2 would surely do. Isn't it?

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