[java] How to modify values of JsonObject / JsonArray directly?

Once i have parsed a JSON String into a GSON provided JsonObject class, (assume that i do not wish to parse it into any meaningful data objects, but strictly want to use JsonObject), how am i able to modify a field / value of a key directly?

I don't see an API that may help me.

https://static.javadoc.io/com.google.code.gson/gson/2.6.2/com/google/gson/JsonObject.html

public static JSONObject convertFileToJSON(String fileName, String username, List<String> list)
            throws FileNotFoundException, IOException, org.json.simple.parser.ParseException {
        JSONObject json = new JSONObject();
        String jsonStr = new String(Files.readAllBytes(Paths.get(fileName)));
        json = new JSONObject(jsonStr);
        System.out.println(json);
        JSONArray jsonArray = json.getJSONArray("users");
        JSONArray finalJsonArray = new JSONArray();
        /**
         * Get User form setNewUser method
         */
        //finalJsonArray.put(setNewUserPreference());
        boolean has = true;
        for (int i = 0; i < jsonArray.length(); i++) {
            JSONObject jsonObject = jsonArray.getJSONObject(i);
            finalJsonArray.put(jsonObject);
            String username2 = jsonObject.getString("userName");
            if (username2.equals(username)) {
                has = true;
            }
            System.out.println("user name  are :" + username2);
            JSONObject jsonObject2 = jsonObject.getJSONObject("languages");
            String eng = jsonObject2.getString("Eng");
            String fin = jsonObject2.getString("Fin");
            String ger = jsonObject2.getString("Ger");
            jsonObject2.put("Eng", "ChangeEnglishValueCheckForLongValue");
            System.out.println(" Eng : " + eng + "  Fin " + fin + "  ger : " + ger);
        }
        System.out.println("Final JSON Array \n" + json);
        jsonArray.put(setNewUserPreference());
        return json;
    }

This works for modifying childkey value using JSONObject. import used is

import org.json.JSONObject;

ex json:(convert json file to string while giving as input)

{
    "parentkey1": "name",
    "parentkey2": {
     "childkey": "test"
    },
}

Code

JSONObject jObject  = new JSONObject(String jsoninputfileasstring);
jObject.getJSONObject("parentkey2").put("childkey","data1");
System.out.println(jObject);

output:

{
    "parentkey1": "name",
    "parentkey2": {
     "childkey": "data1"
    },
}

It's actually all in the documentation.
JSONObject and JSONArray can both be used to replace the standard data structure.
To implement a setter simply call a remove(String name) before a put(String name, Object value).

Here's an simple example:

public class BasicDB {

private JSONObject jData = new JSONObject;

public BasicDB(String username, String tagline) {
    try {
        jData.put("username", username);
        jData.put("tagline" , tagline);
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public String getUsername () { 
    String ret = null;
    try {
        ret = jData.getString("username");
    } catch (JSONException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    } 
    return ret;
}

public void setUsername (String username) { 
    try {
        jData.remove("username");
        jData.put("username" , username);
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public String getTagline () {
    String ret = null;
    try {
        ret = jData.getString("tagline");
    } catch (JSONException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    } 
    return ret;
}

Another approach would be to deserialize into a java.util.Map, and then just modify the Java Map as wanted. This separates the Java-side data handling from the data transport mechanism (JSON), which is how I prefer to organize my code: using JSON for data transport, not as a replacement data structure.

Since 2.3 version of Gson library the JsonArray class have a 'set' method.

Here's an simple example:

JsonArray array = new JsonArray();
array.add(new JsonPrimitive("Red"));
array.add(new JsonPrimitive("Green"));
array.add(new JsonPrimitive("Blue"));

array.remove(2);
array.set(0, new JsonPrimitive("Yelow"));