Why is this JFrame not being sized right?

Question

for some reason, this JFrame is drawing 500 by 470 pixels. It's throwing off my calculations, even on the most basic scale. The code is so basic, I would think it would be accurate. Am I just missing something obvious here? It seems like setSize has always worked before, so what is diferent. Can I not use game.WINDOW_WIDTH?

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

public class Game extends JPanel implements KeyListener, MouseListener {

    //Gamestate stats
    int level = 0; // 0 is menu, 1 is options, 2 is win, 3 is death, 4 is level 1

    final String WINDOW_TITLE = "Platformer a.v.0.1"; // window stats
    final int WINDOW_WIDTH = 500;
    final int WINDOW_HEIGHT = 500;

    int mouseX; // stats for mouse, keyboard, ect
    int mouseY;

    // Level 0 buttons, parameters, ect
    int lv0ButtonOneX = WINDOW_WIDTH/4;
    int lv0ButtonOneY = WINDOW_WIDTH/2;
    int lv0ButtonOneS = 50;

    public static void main(String[] args) {
        Game game = new Game();

        JFrame window = new JFrame(game.WINDOW_TITLE);
        window.setSize(game.WINDOW_WIDTH,game.WINDOW_HEIGHT);
        window.setVisible(true);
        window.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        window.add(game);
        game.addKeyListener(game);
        game.addMouseListener(game);
        game.requestFocusInWindow();

        window.setLocationRelativeTo(null);
        while(true) {
            game.repaint();
            game.customUpdate();
        }
    }

    public void customUpdate() {
        if(level == 0) {
            if(mouseX > lv0ButtonOneX &&
                    mouseX < lv0ButtonOneX + lv0ButtonOneS &&
                    mouseY < lv0ButtonOneY + lv0ButtonOneS &&
                    mouseY > lv0ButtonOneY) {
                level = 4;
            }
        }
    }

    public void paint(Graphics g) {
        if(level == 0) {
            g.setColor(Color.BLACK);
            g.fillRect(0,0,WINDOW_WIDTH,WINDOW_HEIGHT); // draw window          needs to be first in order to be drawn over

            g.setColor(Color.ORANGE);
            g.fillRect(lv0ButtonOneX,lv0ButtonOneY,lv0ButtonOneS,lv0ButtonOneS); // draw buttons

            g.setColor(Color.BLUE);
            g.drawString("Start",lv0ButtonOneX + lv0ButtonOneS/4,lv0ButtonOneY + lv0ButtonOneS/2);
        }
        if(level == 4) {
            g.setColor(Color.GREEN);
            g.fillRect(0,0,WINDOW_WIDTH,WINDOW_HEIGHT); // draw window          needs to be first in order to be drawn over

            g.setColor(Color.ORANGE);
            g.fillRect(0,WINDOW_HEIGHT-20,WINDOW_WIDTH,20); // creates floor at bottom - 20 for standing.
        }
    }

    @Override
    public void keyTyped(KeyEvent e) {

    }

    @Override
    public void keyPressed(KeyEvent e) {

    }

    @Override
    public void keyReleased(KeyEvent e) {

    }

    @Override
    public void mouseClicked(MouseEvent e) {

    }

    @Override
    public void mousePressed(MouseEvent e) {
        mouseX = e.getX();
        mouseY = e.getY();
    }

    @Override
    public void mouseReleased(MouseEvent e) {

    }

    @Override
    public void mouseEntered(MouseEvent e) {

    }

    @Override
    public void mouseExited(MouseEvent e) {

    }
}

Answer 1

Problem:

    window.setSize(game.WINDOW_WIDTH,game.WINDOW_HEIGHT);
    window.setVisible(true);
    window.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);


    window.add(game);
    game.addKeyListener(game);
    game.addMouseListener(game);
    game.requestFocusInWindow();

Solution:

    window.setSize(game.WINDOW_WIDTH,game.WINDOW_HEIGHT);
    window.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    window.add(game);
    game.addKeyListener(game);
    game.addMouseListener(game);
    game.requestFocusInWindow();

    window.setVisible(true);

Do not make the JFrame visible before adding Objects to it.