There is an answer of your question: https://stackoverflow.com/a/17037364/1979882

ArrayList<String> listdata = new ArrayList<String>();     
JSONArray jArray = (JSONArray)jsonObject; 
if (jArray != null) { 
   for (int i=0;i<jArray.length();i++){ 
    listdata.add(jArray.get(i).toString());
   } 
} 

Let us assume that the class is Data with two objects name and dob which are both strings.

Initially, check if the list is empty. Then, add the objects from the list to a JSONArray

JSONArray allDataArray = new JSONArray();
List<Data> sList = new ArrayList<String>();

    //if List not empty
    if (!(sList.size() ==0)) {

        //Loop index size()
        for(int index = 0; index < sList.size(); index++) {
            JSONObject eachData = new JSONObject();
            try {
                eachData.put("name", sList.get(index).getName());
                eachData.put("dob", sList.get(index).getDob());
            } catch (JSONException e) {
                e.printStackTrace();
            }
            allDataArray.put(eachData);
        }
    } else {
        //Do something when sList is empty
    }
    

Finally, add the JSONArray to a JSONObject.

JSONObject root = new JSONObject();
    try {
        root.put("data", allDataArray);
    } catch (JSONException e) {
        e.printStackTrace();
    }

You can further get this data as a String too.

String jsonString = root.toString();

You have to directly construct JSONArray from JSON string in this case.

JSONArray arr = new JSONArray(jstring);

You can customize a little bit of code like it

public static void main(String[] args) throws ParseException {
        String data = "{\"data\":[\"str1\", \"str2\", \"str3\"]}";
        JSONObject json = new JSONObject(
                data);
         
        JSONArray jasonArray = json.getJSONArray("data");
        List list = new ArrayList();

        int size = jasonArray.length();
        int i = 0;
        while (i < size) {
            list.add(jasonArray.get(i));
            i++;
        }

        System.out.println(list);

    }

Here a solution using com.fasterxml.jackson

Person.java:

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.util.List;

class Person  {
    final public String name;
    final public List<String> alsoKnownAs;

    @JsonCreator
    public Person(
            @JsonProperty("name") final String name,
            @JsonProperty("alsoKnownAs") final List<String> alsoKnownAs
    ) {
        this.name = name;
        this.alsoKnownAs = alsoKnownAs;
    }

    public static Person parsePersonJson(String json) {
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            return objectMapper.readValue(json, Person.class);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

Here a quick test:

PersonTest.java

import org.junit.Test;

public class PersonTest {


    @Test
    public void parseAJsonToAPerson() {
        String json = "{\"name\":\"moses\",\"alsoKnownAs\":[\"njai\", \"njenga\",\"musa\"]}";
        Person currentPerson = Person.parsePersonJson(json);

        System.out.println("name: " + currentPerson.name);
        System.out.println("alsoKnownAs: " + currentPerson.alsoKnownAs);

    }

}

Test output is:

name: moses
alsoKnownAs: [njai, njenga, musa]

For any one who looks for answer yet:

1.Add jackson-databind library to your build tools like Gradle or Maven

2.in your Code:

ObjectMapper mapper = new ObjectMapper();

List<Student> studentList = new ArrayList<>();

studentList = Arrays.asList(mapper.readValue(jsonStringArray, Student[].class));