You need an external library for this.

JSONArray jsonA = JSONArray.fromObject(mybeanList);
System.out.println(jsonA);

Google GSON is one of such libraries

You can also take a look here for examples on converting Java object collection to JSON string.

public static List<Product> getCartList() {

    JSONObject responseDetailsJson = new JSONObject();
    JSONArray jsonArray = new JSONArray();

    List<Product> cartList = new Vector<Product>(cartMap.keySet().size());
    for(Product p : cartMap.keySet()) {
        cartList.add(p);
        JSONObject formDetailsJson = new JSONObject();
        formDetailsJson.put("id", "1");
        formDetailsJson.put("name", "name1");
       jsonArray.add(formDetailsJson);
    }
    responseDetailsJson.put("forms", jsonArray);//Here you can see the data in json format

    return cartList;

}

you can get the data in the following form

{
    "forms": [
        { "id": "1", "name": "name1" },
        { "id": "2", "name": "name2" } 
    ]
}

You can also direct use

 String jsonString = new ObjectMapper().writeValueAsString(jsonObjectList) 

To get the desired ouptput

Here is the small example

List<JSONObject> jsons = new ArrayList<>();
jsons.add(new JSONObject(ImmutableMap.of("Attribute", "EmailAddress", "Value", "abc@yahoo.com")));
jsons.add(new JSONObject(ImmutableMap.of("Attribute1", "EmailAddress3", "Value1", "abc@yahoo.com1")));
System.out.println(new ObjectMapper().writeValueAsString(jsons));

The output is

[{"Value":"abc@yahoo.com","Attribute":"EmailAddress"},{"Attribute1":"EmailAddress3","Value1":"abc@yahoo.com1"}]

I suspect there are some toString() method in any object that you have override?

If you want just to convert the list to json, you can use Gson:

List<Integer> myList = new ArrayList<>();
myList.add(1);
myList.add(2);
String json = new Gson().toJson(myList);

If you want that the key will be "List", you need to create a object with a member that call List and then convert it.

Here is the piece of code which you need

package uk.co.vishal;

import com.fasterxml.jackson.core.JsonProcessingException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Answer {

public static void main(String[] args) throws JsonProcessingException {
    List<String> data = new ArrayList<>();
    data.add("user");
    data.add("car");
    data.add("brand");

    System.out.println(data.toString());

    Map<String, String> mydata = new HashMap<>();
    Map<String, JSONObject> newdata = new HashMap<>();
    JSONObject result = new JSONObject();
    boolean flag = true;

    for (int i = data.size() - 1; i >= 0; i--) {
        if (flag) {
            mydata.put(data.get(i), "BMW");
            result = generateJson(mydata);
            flag = false;
        } else {
            newdata.put(data.get(i), result);
            result = generateJson(newdata);
            newdata.clear();
        }
    }
    System.out.println(result);
    /*
    * Here is the output:
    * {
        "user": {
            "car": {
                    "brand": "BMW"
                }
            }
      }
    *
    * */
}

private static JSONObject generateJson(Map data) {
    return new JSONObject(data);
}

}

I hope you will be sorted !!