JSON数组到ArrayList <List<String> &gt;

Question

I have an JSON Array that looks like this

[["ONE","CAT",0],["TWO","DOG",0]]

And I want to make it into an ArrayList<List<String>> , I am trying to loop though it but can't get it to work.

I have tried

for (ArrayList arrayList: jsonArray) {
                for (Object array : arrayList) {

                }
            }

But then I got a compilation error. I'm not able to loop through an Array of JSON Objects.

Answer 1

You can try this way -

try {
        ArrayList<Object> _arrList = new ArrayList<Object>();
        JSONArray _jArryMain = new JSONArray("YOUR_JSON_STRING");
        if (_jArryMain.length()>0) {
            for (int i = 0; i < _jArryMain.length(); i++) {
                JSONArray _jArraySub  = _jArryMain.getJSONArray(i);
                _arrList.add(_jArraySub);

            }
        }
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

Answer 2

First, Java does not like mixed types. If you are sure you can use List<List<String>> then keep reading.

I recommend using the Jackson Library and ObjectMapper#readTree .

ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.readTree("JSON CONTENT");
List<List<String>> convertedList = new ArrayList<List<String>>();
for (JsonNode arrNode : node) {
    List<String> currList = new ArrayList<String>();
    convertedList.add(currList);
    for (JsonNode dataNode : arrNode) {
        currList.add(dataNode.asText());
    }
}
System.out.println(convertedList);

Answer 3

I guess this is what your looking for :

try {
        ArrayList<ArrayList<Object>> mainarraylist = new ArrayList<ArrayList<Object>>();
        JSONArray jsonarray = new JSONArray(yourstringjson);
        if (jsonarray.length()>0) {
            for (int i = 0; i < jsonarray.length(); i++) {
               ArrayList<String> subarray;
               JSONArray jsonsubarray  = jsonarray.getJSONArray(i);
               for (int i = 0; i < jsonsubarray.length(); i++) {
                 subarray = new ArrayList<String>;

                 jsonsubarray.add(jsonsubarray.get(i));
             }
           mainarraylist.add(jsonsubarray);
            }
        }
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

This will give you the result: mainarraylist.get(0).get(0) equals ONE

FYI: The code is not compiled, so there might some errors. This is an abstract for your solution.

Answer 4

you can use this code to solve your problems

String jsonValue = "[[\"ONE\",\"CAT\",0],[\"TWO\",\"DOG\",0]]";
  try{
  JSONArray array = (JSONArray) new JSONTokener(jsonValue).nextValue();
  ArrayList<JSONArray> arrayList = new ArrayList<>();
  arrayList.add(array);
  for (int i=0;i<arrayList.get(arrayList.size()-1).length();i++) {
        try {
            JSONArray arr = arrayList.get(arrayList.size()-1).getJSONArray(i);
            for (int j = 0; j < arr.length(); j++) {
                System.out.println("Value = " + arr.get(j));
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
  }catch (JSONException e){

  }

Answer 5

 1. try {
                String abc = "[[\"ONE\",\"CAT\",0],[\"TWO\",\"DOG\",0]]";
                JSONArray jsonarray = new JSONArray(abc);
                if (jsonarray.length()>0) {
                    for (int i = 0; i < jsonarray.length(); i++) {
                        JSONArray jsonsubarray  = jsonarray.getJSONArray(i);
                        for (int j = 0; j < jsonsubarray.length(); j++) {


                           Log.d("Value---->",""+jsonsubarray.get(j));
                        }

                    }
                }
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

Answer 6

To parse a json array to a list of list i have created the following method.

public static List<List<String>> convertJsonToListofList(String json) throws Exception{
    JSONArray jArray=new JSONArray(json);
    List<List<String>> list = new ArrayList<List<String>>();     
    int length = jArray.length();
    for(int i=0; i<length;i++) {
        JSONArray array;
        List<String> innerlist = new ArrayList<String>();
        String innerJsonArrayString = jArray.get(i).toString();
        JSONArray innerJsonArray = new JSONArray(innerJsonArrayString);
        int innerLength = innerJsonArray.length();
        for(int j=0;j<innerLength;j++){
            String str = innerJsonArray.getString(j);
            innerlist.add(str);
        }
        list.add(innerlist);      
    }
    return list;
}

You have to call this method in this way:

try {
        List<List<String>> listoflist = convertJsonToListofList("[[\"ONE\",\"CAT\",0],[\"TWO\",\"DOG\",0]]");
        System.out.println(listoflist);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

The output I have obtained is this one

07-09 13:00:42.268: I/System.out(19986): [[ONE, CAT, 0], [TWO, DOG, 0]]

I hope this is what you are looking for :)

Answer 7

Another Jackson approach.

ObjectMapper mapper = new ObjectMapper();
String json = "[[\"ONE\",\"CAT\",0],[\"TWO\",\"DOG\",0]]";
List<List<String>> output = new ArrayList<List<String>>();

JsonNode root = mapper.readTree(json);
for (JsonNode child : root) {
    output.add(mapper.readValue(child.traverse(), new TypeReference<ArrayList<String>>(){}));
}