мое приложение выглядит так, я получаю исключение нулевого указателя в методе draw (), если быть точным в g.drawImage (img, 0, 0, null)

package com.ochs.game;

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Game extends JPanel implements Runnable{
private static final long serialVersionUID = 8229934361462702491L;

public static final int WIDTH = 320;
public static final int HEIGHT = 240;
public static final int SCALE = 2;

public boolean isRunning;

private BufferedImage img;
private Graphics2D g2d;

public Game() {
    setFocusable(true);
    requestFocus();
    start();
}

public void start() {
    isRunning = true;
    new Thread(this).start();
}

public void stop() {
    isRunning = false;
}

public void run() {
    long start;
    init();
    while(isRunning) {
        start = System.currentTimeMillis();

        update();
        render();
        draw();

        try {
            Thread.sleep(5 - (System.currentTimeMillis() - start));
        } catch (Exception e) {
        }
    }
}

public void init() {
    img = new BufferedImage(WIDTH*SCALE, HEIGHT*SCALE, BufferedImage.TYPE_INT_RGB);
    g2d = (Graphics2D) img.getGraphics();
}

public void update() {

}

public void render() {

}

public void draw() {
    Graphics g = getGraphics();
    g.drawImage(img, 0, 0, null);    // < getting null pointer here!
}

public static void main(String[] args) {
    Dimension size = new Dimension(WIDTH*SCALE, HEIGHT*SCALE);
    Game gameComponent = new Game();
    JFrame frame = new JFrame();
    frame.setVisible(true);
    frame.setSize(size);
    frame.setLocationRelativeTo(null);
    frame.setResizable(false);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(gameComponent);
}
}