GameEngine for updating image

 import com.sun.imageio.plugins.jpeg.JPEGImageMetadataFormatResources;

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;

public class Window {
    private Canvas canvas;
    private JFrame frame;
    private BufferedImage image;
    private BufferStrategy bs;
    private Graphics g;

    public Window() {
        image = new BufferedImage(GameContainer.w , GameContainer.h ,BufferedImage.TYPE_INT_RGB);

        canvas = new Canvas();
        Dimension dimension = new Dimension(GameContainer.w * GameContainer.scale,
                GameContainer.h * GameContainer.scale);
        canvas.setPreferredSize(dimension);
        canvas.setMinimumSize(dimension);
        canvas.setMaximumSize(dimension);

        frame = new JFrame(GameContainer.title);
        frame.setPreferredSize(dimension);
        frame.setLayout(new BorderLayout());
        frame.add(canvas, BorderLayout.CENTER);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        canvas.createBufferStrategy(2); //This should be after JFrame
        bs = canvas.getBufferStrategy();
        g = bs.getDrawGraphics();
    }

    public void update() {
        g.drawImage(image, canvas.getWidth(), canvas.getHeight(), null);
        bs.show();
    }
}