Thread: Timer that could work when is closed doesn't work correctly

Hello, I made a timer that shows an image when the time runs out, but I wanna make it work when I close the program and when I open it again, the time still running, for that I save the current miliseconds when the timer was started and the remaining time and if the time is running in a JSON file when I close the window and thus stopping the program, and read that data when I re-run the program
But when I close the window when the timer is running the program is still running and I have to force the stop, the JSON file is still written, but when I re-run the program, the timer appears as finished when it shouldn't, what's wrong?

import org.json.JSONObject;
import org.json.JSONTokener;
 
import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.io.*;
import java.nio.file.Files;
import java.nio.file.Paths;
 
public class Temporizador extends JFrame {
    private static final int DELAY = 10; // Milésimas de segundo
    private static final long TIEMPO = 86400000/DELAY; // En centésimas de segundo
    // Edit these if you wanna test it
    private static final String ROUTE = "C:\\Users\\SEBAS\\Documents\\NetBeansProjects\\OtroTemporizador";
    private static final String IMAGEN = ROUTE + "\\Imagenes\\Imagen.jpg";
    private static final String DATA = ROUTE + "\\Data\\Data.json";
 
    private final JButton iniciar;
    private final JLabel imagen;
 
    private Timer reloj;
    private long tiempoRestante;
    private Data data;
 
    public static void main(String[] args) {
        new Temporizador();
    }
 
    private Temporizador() {
        data = readFile();
 
        setTitle("Temporizador");
        setSize(800, 600);
        setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
        setResizable(false);
        setLocationRelativeTo(null);
 
        JPanel panel = new JPanel();
        panel.setLayout(null);
 
        imagen = new JLabel();
        imagen.setLocation(0, 90);
        imagen.setSize(600, 510);
        imagen.setPreferredSize(new Dimension(600, 510));
        imagen.setOpaque(true);
        imagen.setBackground(Color.WHITE);
        imagen.setFont(new Font("Courier", Font.BOLD,75));
 
        iniciar = new JButton();
        iniciar.setText("Correr");
        iniciar.setLocation(0, 0);
        iniciar.setSize(100, 30);
        iniciar.setPreferredSize(new Dimension(100, 30));
        iniciar.setVisible(true);
        iniciar.addActionListener((event) -> {
            startTimer(TIEMPO);
        });
 
        panel.add(imagen);
        add(iniciar);
        add(panel);
 
        // Guardar y/o checkear que se halla guardado información
 
        if (data.running) {
            startTimer((data.remaining - (System.currentTimeMillis() - data.start)) / DELAY);
        }
 
        addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                if (data.running) {
                    data.remaining = tiempoRestante * DELAY;
                    writeFile(data);
                }
                else {
                    writeFile(new Data());
                }
                e.getWindow().dispose();
            }
        });
 
        setVisible(true);
    }
 
    private void startTimer(long time) {
        tiempoRestante = time;
        data.running = true;
        data.start = System.currentTimeMillis();
        reloj = new Timer(DELAY, (e) -> {
            updateTiempo();
            if (tiempoRestante <= 0) {
                reloj.stop();
                data.running = false;
                showImage();
            }
        });
        reloj.start();
    }
 
    private void showImage() {
        File file = new File(IMAGEN);
        try {
            BufferedImage bufferedImage = ImageIO.read(file);
            imagen.setIcon(new ImageIcon(bufferedImage));
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
 
    private static final int secDiv = 1000/DELAY;
    private static final int minDiv = 60 * secDiv;
    private static final int hourDiv = 60 * minDiv;
 
    private void updateTiempo() {
        tiempoRestante--;
        long cent = tiempoRestante % secDiv;
        long sec = (tiempoRestante / secDiv) % 60;
        long min = (tiempoRestante / minDiv) % 60;
        long hours = (tiempoRestante/ hourDiv);
 
        imagen.setText((hours < 10 ? "0" : "") + hours + ":" + (min < 10 ? "0" : "") + min + ":" + (sec < 10 ? "0" : "") + sec + ":" + (cent < 10 ? "0" : "") + cent);
    }
 
    private static class Data {
        long start = 0; // Milisegundos
        long remaining = 0; // Milisegundos
        boolean running = false;
    }
 
    private static Data readFile() {
        File file = new File(DATA);
        Data data = new Data();
 
        if (!file.exists() || file.length() == 0)
            return data;
 
        try {
            JSONTokener parser = new JSONTokener(new FileInputStream(file));
            JSONObject obj = new JSONObject(parser);
 
            data.start = obj.getInt("start");
            data.remaining = obj.getInt("remaining");
            data.running = obj.getBoolean("running");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
 
        return data;
    }
 
    private static void writeFile(Data data) {
        JSONObject obj = new JSONObject();
        obj.put("start", data.start);
        obj.put("remaining", data.remaining);
        obj.put("running", data.running);
 
        try {
            File file = new File(DATA);
            BufferedWriter writer = Files.newBufferedWriter(Paths.get(file.toURI()));
            obj.write(writer);
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Originally Posted by Norm

Should the window closing code stop the timer?

How can the program be execute for testing? It needs a json file.

I don't know if it should, do I try it?
And the json file is automatically created if don't exists, you just need to edit the file routes in the top of the code to test it correctly.

Edit: stopping the timer solved the problem of the program not stopping when I close the window, thanks, but why when I re-run the program, the timer is ended when it shouldn't? Does it have to do with this?

if (data.running) {
    startTimer((data.remaining - (System.currentTimeMillis() - data.start)) / DELAY);
}

Originally Posted by Norm

What values cause the timer to end? Print them out so you can see them.

This is the function of the timer:

private void startTimer(long time) {
    tiempoRestante = time;
    data.running = true;
    data.start = System.currentTimeMillis();
    reloj = new Timer(DELAY, (e) -> {
        updateTiempo();
        if (tiempoRestante <= 0) {
            reloj.stop();
            data.running = false;
            showImage();
        }
    });
    reloj.start();
}

But at the end I found the problem, when I was reading the JSON file, I was getting the start and remaining time as int and not as long:

JSONTokener parser = new JSONTokener(new FileInputStream(file));
JSONObject obj = new JSONObject(parser);
 
// Incorrect
data.start = obj.getInt("start");
data.remaining = obj.getInt("remaining");
// Correct
data.start = obj.getLong("start");
data.remaining = obj.getLong("remaining");