I am getting a NullPointerException in my game and I don't know why?

[pj6444]

So, I am getting a NullPointerException in the drawToScreen method when I try to draw the image... Does anyone know why?

package com.patrickfeltes.game;

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

import javax.swing.JPanel;

public class GamePanel extends JPanel implements Runnable {

	public static final int WIDTH = 400;
	public static final int HEIGHT = 300;
	public static final int SCALE = 2;
	
	public static boolean isRunning = false;
	
	private Thread thread;
	
	private static final int targetFPS = 60;
	private long targetTime = 1000 / targetFPS;
	
	private BufferedImage image;
	
	private Graphics g, g2;
	
	public GamePanel() {
		setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE));
		
		start();
	}
	
	public void start() {
		isRunning = true;
		thread = new Thread(this);
		thread.start();
	}


	public void run() {
		
		image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
		
		long start;
		long elapsed;
		long wait;
		
		while(isRunning) {
			start = System.nanoTime();
			
			tick();
			draw();
			drawToScreen();
			
			elapsed = System.nanoTime() - start;
			wait = targetTime - elapsed;
			
			if(wait < 0) {
				wait = 17;
			}
			
			try {
				Thread.sleep(wait);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
	
	public void tick() {
		
	}
	
	public void draw() {
		g = image.getGraphics();
		g.fillRect(10, 10, 10, 10);
		
	}
	
	public void drawToScreen() {
		g2 = getGraphics();
		g2.drawImage(image, 0, 0, WIDTH * SCALE, HEIGHT * SCALE, null);
	}
	
	
	
}

[SurfMan]

The stacktrace should tell you exactly which line it occurred. The only possible line that could cause this is line 81 in your example. So put a System.out.println() in there to see if g2 is null. If it is, find out why getGraphics() returns null. I think this code is run without the JPanel being visible.

[Norm]

You forgot to paste the full text of the error message.

You get a NPE when trying to execute a statement with a variable with a null value.
Read the API doc for the NullPointerException class for a fuller explanation.

[pj6444]

I tried the System.out.println() and the first two statements were null, but after that it was fine. Should I initialize the g2 earlier?

[Norm]

Why not override the paintComponent() method and use the Graphics object passed to it to do the drawing?