Applet example: drawing a house with back buffering

import java.awt.*;
import javax.swing.*;
import java.awt.Graphics;
/**
 * This will draw a simple house in an Applet at a location
 * specified in the void method init manipulated by the xAxis
 * and yAxis variables
 *
 * @author Shaun B
 * @version 2012-10-31
 */
public class House extends JApplet
{
    // This array will draw a simple house:
    private static int house[] =
    {
        100, 10,  80, 20,
         80, 20, 120, 20,
        120, 20, 100, 10,
         90, 20,  90, 50,
        110, 20, 110, 50,
         90, 50, 110, 50,
        -1
    };
    // This will be used to get the width and height of the Applet
    private int width=0;
    private int height=0;
    // This will be used to index through the array above:
    private int index=0;
    // Read up about back buffering, as it's important ;-)
    private Image backBuffer = null;
    private Graphics backg = null;
     /**
     * Called by the browser or applet viewer to inform this JApplet that it
     * has been loaded into the system. It is always called before the first
     * time that the start method is called.
     */
    @Override
    public void init()
    {
        // this is a workaround for a security conflict with some browsers
        // including some versions of Netscape & Internet Explorer which do
        // not allow access to the AWT system event queue which JApplets do
        // on startup to check access. May not be necessary with your browser.
        JRootPane rootPane = this.getRootPane();
        rootPane.putClientProperty("defeatSystemEventQueueCheck", Boolean.TRUE);
        // provide any initialisation necessary for your JApplet
        // Gets the current width and height and creates a back buffer
        // to that height:
        width = getSize().width;
        height = getSize().height;
        backBuffer = createImage(width, height);
        // Creates instance of the back buffer:
        backg = backBuffer.getGraphics();
        // Sets default behaviour as focusable:
        setFocusable(true);
        // Alter this to move the position of the house:
        int xAxis = 100;
        int yAxis = 100;
        // Calls the method to draw the house:
        drawHouse(xAxis, yAxis);
        // Calls repaint to flip the buffers:
        repaint();
    }
    public void drawHouse(int x, int y)
    {
        // This will step through the array positions to draw
        // the house:
        while(house[index]>=0)
        {
            int x0 = x+(house[index+0]);
            int y0 = y+(house[index+1]);
            int x1 = x+(house[index+2]);
            int y1 = y+(house[index+3]);
            backg.drawLine( x0, y0, x1, y1 );
            index += 4;
        }
        // Resets index to zero, incase the JApplet is reloaded or something:
        index = 0;
    }
    /**
     * Called by the browser or applet viewer to inform this JApplet that it
     * should start its execution. It is called after the init method and
     * each time the JApplet is revisited in a Web page.
     */
    @Override
    public void start()
    {
        // Call to parent:
        super.start();
    }
    /**
     * Called by the browser or applet viewer to inform this JApplet that
     * it should stop its execution. It is called when the Web page that
     * contains this JApplet has been replaced by another page, and also
     * just before the JApplet is to be destroyed.
     */
    @Override
    public void stop()
    {
        // Call to parent:
        super.stop();
    }
    // Main paint method (called on repaint(); I think):
    @Override
    public void paint(Graphics g)
    {
        // Calls to the update method:
        update(g);
    }
    public void update(Graphics g)
    {
        // Gets the backBuffer and draws it to the canvas:
        g.drawImage(backBuffer,0,0,this);
        // the sync toolkit is used for animations as it stops flicker:
        getToolkit().sync();
    }
    /**
     * Called by the browser or applet viewer to inform this JApplet that it
     * is being reclaimed and that it should destroy any resources that it
     * has allocated. The stop method will always be called before destroy.
     */
    @Override
    public void destroy()
    {
        // Calls the garbage collector before calling parent:
        System.gc();
        super.destroy();
    }
}