Game loop, is this one good?

[raxell]

Hi, what do you think about this game loop? The code is taken from a youtube tutorial.
I’ve read a lot of articles about game loop and timesteps (including the thread on this forum: http://www.java-gaming.org/index.php?topic=24220.0), but I don’t understand when the cpu is highly used.
I think this code is good, but i don’t know if the cpu can be stressed using it (i don’t see any Thread.sleep() in the code).
Can you say me if there are important problems?

package engine.test.game;

import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;

public class Game extends Canvas implements Runnable
{
    private static final long serialVersionUID = 1L;
    
    public static final int WIDTH = 100;
    public static final int HEIGHT = 60;
    public static final int SCALE = 6;
    public static final String TITLE = "Game";
    
    private Thread thread;
    private JFrame frame;
    private boolean running = false;
    
    private Screen screen;
    
    private BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
    private int[] pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
    
    public Game()
    {
        Dimension size = new Dimension(WIDTH * SCALE, HEIGHT * SCALE);
        setPreferredSize(size);
        
        screen = new Screen(WIDTH, HEIGHT);
        
        frame = new JFrame();
    }
    
    public synchronized void start()
    {
        running = true;
        
        thread = new Thread(this, "Game");
        thread.start();
    }
    
    public synchronized void stop()
    {
        running = false;
        
        try {
            thread.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    
    public void run()
    {
        long now = 0;
        long timer = System.currentTimeMillis();
        long startTime = System.nanoTime();
        long lastTime = System.nanoTime();
        long stopTime = System.nanoTime() + 5000000000L;
        double ns = 1000000000 / 60;
        double delta = 0;
        int updates = 0;
        int frames = 0;
        
        // execute for a fixed time, i don't need to execute it more than some minutes
        while (now <= stopTime) {
            now = System.nanoTime();
            delta += (now - lastTime) / ns;
            lastTime = now;
            while (delta >= 1) {
                update();
                updates++;
                delta--;
            }
            render();
            frames++;
            
            if (System.currentTimeMillis() - timer > 1000) {
                timer += 1000;
                System.out.println(updates + " upd, " + frames + " fps");
                frame.setTitle(TITLE + " | " + updates + " upd, " + frames + " fps");
                updates = 0;
                frames = 0;
            }
        }
        
        long endTime = System.nanoTime();
        System.out.println("Duration: " + ((endTime - startTime)/1000000) + "ms");
        
        stop();
    }
    
    public void update()
    {
        
    }
    
    public void render()
    {
        BufferStrategy bs = getBufferStrategy();
        if (null == bs) {
            createBufferStrategy(3);
            
            return;
        }
        
        screen.clear();
        screen.render();
        
        for (int i = 0, l = pixels.length; i < l; i++) {
            pixels[i] = screen.pixels[i];
        }
        
        Graphics g = bs.getDrawGraphics();
        
        g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
        g.dispose();
        bs.show();
    }
    
    public static void main(String[] args)
    {
        Game game = new Game();
        game.frame.setResizable(false);
        game.frame.setTitle(TITLE);
        game.frame.add(game);
        game.frame.pack();
        game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        game.frame.setVisible(true);
        game.frame.setLocationRelativeTo(null);
        
        game.start();
    }
}

Thanks in advance and sorry for my bad english (correct me if you note mistake).