GameLoop

import java.awt.*;
import java.util.*;
import java.awt.image.*;
import javax.swing.JFrame;

public class TestLoop extends Canvas implements Runnable{

    private static final int WIDTH = 800;
    private static final int HEIGHT = 600;
    private boolean running = false;
    private int tick;
    private int frames;
    private int tickCount;

    private BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
    private int[] pixel = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();

    public void start(){
        if(!running){
            running = true;
            new Thread(this).start();
        }
    }

    public void stop(){
        if(running)running = false;
    }

    public void run(){
        long lastTime = 0;
        double updateInterval = 1000000000.0 / 60.0;
        long nextUpdateTick = System.nanoTime();
        long now = 0;
        long start = 0;
        long timer = System.currentTimeMillis();
        long fps = 60;

        while(running){
            long deltaTime = System.nanoTime() - lastTime;
            lastTime += deltaTime;
            start = System.nanoTime();
            for(now = System.nanoTime(); now > nextUpdateTick; nextUpdateTick += updateInterval){
                tick++;
                update();
            }

            render();
            Toolkit.getDefaultToolkit().sync();


            long sleepTime = Math.round((1e9/fps - (System.nanoTime() - lastTime)) /1e6);
            if(sleepTime < 0)continue;

            long prev = System.nanoTime(), diff;
            while((diff = System.nanoTime() - prev) < sleepTime){
                if(diff < sleepTime * 0.8){
                    try{
                        Thread.sleep(1);
                        } catch(Exception e){
                            e.printStackTrace();
                        }
                } else {
                    Thread.yield();
                }
            }
            if(System.currentTimeMillis() - timer > 1000){
                System.out.println("FPS: " + frames + " Ticks: " + tick);
                frames = 0;
                tick = 0;
                timer += 1000;
            }
        }

    }

    public void update(){
        tickCount++;
    }

    public void render(){
        frames++;
        BufferStrategy bs = getBufferStrategy();
        if(bs == null){
            createBufferStrategy(3);
            return;
        }

        for(int i = 0; i < pixel.length; i++){
            pixel[i] = (i + tickCount);
        }

        Graphics g = bs.getDrawGraphics();
        g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
        g.dispose();
        bs.show();

    }

    public static void main(String[] args){
        TestLoop game = new TestLoop();
        game.setPreferredSize(new Dimension(WIDTH, HEIGHT));
        game.setMaximumSize(new Dimension(WIDTH, HEIGHT));
        game.setMinimumSize(new Dimension(WIDTH, HEIGHT));

        JFrame frame = new JFrame();
        frame.add(game);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        game.start();
    }

}