Java 8: How to write lambda stream to work with JsonArray?

Question

I'm very new to Java 8 lambdas and stuff... I want to write a lambda function that takes a JSONArray, goes over its JSONObjects and creates a list of values of certain field.

For example, a function that takes the JSONArray: [{name: "John"}, {name: "David"}] and returns a list of ["John", "David"].

I wrote the following code:

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;

public class Main {
    public static void main(String[] args) {
        JSONArray jsonArray = new JSONArray();
        jsonArray.add(new JSONObject().put("name", "John"));
        jsonArray.add(new JSONObject().put("name", "David"));
        List list = (List) jsonArray.stream().map(json -> json.toString()).collect(Collectors.toList());
        System.out.println(list);
    }
}

However, I get an error:

Exception in thread "main" java.lang.NullPointerException

DO you know how to resolve it?

Answer 1

Try with IntStream.

List<String> jsonObject = IntStream
       .range(0,jsonArray.size())
       .mapToObj(i -> jsonArray.getJSONObject(i))
       .collect(Collectors.toList());