NullPointerException

Hello,

I recently started following some Java tutorials. (Game Programming series on youtube by TheChernoProject)
I'm now at episode 5 and it's the first time we need to run our code (in debug mode).
I have exactly the same code as the tutor, but i get a Null Pointer Exception error. Can someone please take a look at the code and explain what the problem is?

the code is:

package com.sarranoob.lucid;

import java.awt.Canvas;
import java.awt.Dimension;
import javax.swing.JFrame;

public class Game extends Canvas implements Runnable {

	private static final long serialVersionUID = 1L;
	
	public static int width = 300;
	public static int height = width / 16 * 9;
	public static int scale = 3;
	
	private Thread thread;
	private JFrame frame;
	private boolean running = false;
	
	public Game() {
		Dimension size = new Dimension(width * scale, height * scale);
		setPreferredSize(size);
	}
	
	public synchronized void start() {
		running = true;
		thread = new Thread(this, "Display");
		thread.start();
	}
	
	public synchronized void stop() {
		running = false;
		try{
			thread.join();
		} catch(InterruptedException e) {
			e.printStackTrace();
		}
		
	}
	
	public void run() {
		while (running) {
			System.out.println("Testing...");
		}
	}
	
	public static void main(String[] args) {
		Game game = new Game();
		game.frame.setResizable(false);
		game.frame.setTitle("Lucid Alpha Testing");
		game.frame.add(game);
		game.frame.pack();
		game.frame.setLocationRelativeTo(null);
		game.frame.setDefaultCloseOperation(JFrame.EXIT_ON
_CLOSE);
		game.frame.setVisible(true);
		game.start();
	}

}

and the error:
Exception in thread "main" java.lang.NullPointerException
at com.sarranoob.lucid.Game.main(Game.java:48)

line 48 (where the error occurred) is:
game.frame.setResizable(false);

Thanks on advance.