How to convert list data into json in java

I have a function which is returning Data as List in java class. Now as per my need, I have to convert it into Json Format.

Below is my function code snippet:

public static List<Product> getCartList() {
    List<Product> cartList = new Vector<Product>(cartMap.keySet().size());
    for(Product p : cartMap.keySet()) {
        cartList.add(p);
    }
    return cartList;
}

I tried To convert into json by using this code but it is giving type mismatch error as function is of type List…

public static List<Product> getCartList() {
    List<Product> cartList = new Vector<Product>(cartMap.keySet().size());
    for(Product p : cartMap.keySet()) {
        cartList.add(p);
    }

    Gson gson = new Gson();
     // convert your list to json
     String jsonCartList = gson.toJson(cartList);
     // print your generated json
     System.out.println("jsonCartList: " + jsonCartList);

     return jsonCartList;

        }

Please help me resolve this.

Answer

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" } 
    ]
}