Thread: Dont understand the nullpointerexception

package src;
 
import javax.swing.JFrame;
import java.awt.Graphics;
 
public class GameApplet extends JFrame {
 
	public static GameApplet client;
 
	public GameApplet() {
		setTitle("GameApplet - Alpha 1.0.0");
		setSize(1000, 1000);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setResizable(false);
		setVisible(true);
	}
 
	public static void createTiles(int X, int Y, int Height, int Width) {
		client.paint(null, X, Y, Height, Width);
	}
 
	public void paint(Graphics g, int X, int Y, int Height,  int Width) {
           g.drawRect(X, Y, Height, Width);
    }
	public static void main(String[] args) {
		createTiles(100, 100, 300, 300);
	}
}
 
I understand the nullpointerexception means I have a null value but don't understand where

Originally Posted by PhHein

public static void createTiles(int X, int Y, int Height, int Width) {
	client.paint(null, X, Y, Height, Width);
}

client is null. You've never instanciated it, but I don't see why you need that anyway.

I got rid of that to make this:

public static GameApplet client;
 
	public GameApplet() {
		setTitle("GameApplet - Alpha 1.0.0");
		setSize(1000, 1000);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setResizable(false);
		setVisible(true);
	}
 
	public static void createTiles(int X, int Y, int Height, int Width) {
		paint(null, X, Y, Height, Width);
	}
 
	public static void paint(Graphics g, int X, int Y, int Height,  int Width) {
           g.drawRect(X, Y, Height, Width);
    }
	public static void main(String[] args) {
		createTiles(100, 100, 300, 300);
	}
}

Yet the same error still occurs.

Points of interest are lines:
at src.GameApplet.paint(GameApplet.java:23)
at src.GameApplet.createTiles(GameApplet.java:19)
at src.GameApplet.main(GameApplet.java:26)

Originally Posted by PhHein

You call paint with null as the first parameter. This cannot work.

Hmm, it worked when I wrote it differently yesterday. What parameter for graphics should it be? Only just started graphic methods/stuff.