JSONDemo

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

public class JSONDemo {
    public final static String FILE_NAME = "JSONDemo2.json";
    public static void main(String[] args) {
        jsonToFile(FILE_NAME);

        String jsonString = jsonFromFile(FILE_NAME);

        jsonParse(jsonString);
    }

    @SuppressWarnings("unchecked")
    public static void jsonToFile(String fileName) {
        String name = Svetovid.in.readLine("Enter a name: ");
        JSONObject root = new JSONObject();
        root.put("name", name);

        JSONArray courses = new JSONArray();

        while(true) {
            String course = Svetovid.in.readLine("Enter a course name (Enter to exit): ");
            if (course.length() == 0)
                break;

            int grade = Svetovid.in.readInt("Enter a course grade: ");

            JSONObject courseObject = new JSONObject();
            courseObject.put("grade", grade);
            courseObject.put("course", course);
            courses.add(courseObject);
        }
        root.put("courses", courses);

        File file = new File(fileName);

        try (PrintWriter writer = new PrintWriter(file)) {
            writer.print(root.toJSONString());
        } catch (FileNotFoundException e) {
            System.err.println(e.toString());
        }

        System.out.println("File created successfully.\n");
    }

    public static String jsonFromFile(String fileName) {
        StringBuilder jsonIn = new StringBuilder();

        while (Svetovid.in(fileName).hasMore()) {
            jsonIn.append(Svetovid.in(fileName).readLine());
        }

        return jsonIn.toString();
    }

    public static void jsonParse(String jsonString) {
        JSONParser parser = new JSONParser();

        try {
            JSONObject root = (JSONObject) parser.parse(jsonString);
            System.out.printf("Course info for %s", root.get("name") + "\n");

            JSONArray courses = (JSONArray) root.get("courses");

            for (int i = 0; i < courses.size(); i++) {
                JSONObject course = (JSONObject) courses.get(i);

                System.out.printf("course: %s", course.get("course") + ", ");
                System.out.printf("grade: %d", course.get("grade"));
                System.out.println();
            }
        } catch (ParseException e) { System.err.println(e); }
    }
}