[adam405]

I am trying to create a bouncing ball. At the momene the ball just travels off the applet screen instead of bouncing back. Any help is appreciated.

Code:

// import necessary packages
import java.applet.*;
import java.awt.*;
import java.util.Random;


public class FirstApplet extends Applet implements Runnable
{
    //position of the ball
    int x_pos = 1;
    int y_pos = 1;
    int first_x =1;
    int first_y =1;
   
    //ball size
    int radius = 5;
    
    //direction
    int x_speed = 1;
    int y_speed = 1;
    
    //applet size
    int appletsize_top = 10;
    int appletsize_bottom = 370;  
    int appletsize_left = 10;  
    int appletsize_right = 370;  
    //random movement
    Random rnd = new Random ();
    
    //Drawing image off screen
    private Image dbImage;
    private Graphics dbg;
    
    int maxspeed = 1;

// start - method is called every time you enter the HTML 
public void start ()
{
// define a new thread 
Thread th = new Thread (this);
// start this thread
th.start ();
}

	
	
//run- start the applet game
public void run () 
{ 
    while (true)
    {
    // lower ThreadPriority 
    Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
    //change direction if ball hits right side
 
    if (x_pos > appletsize_left)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        }

    else if (x_pos < appletsize_right)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        }      
    
    else if (y_pos > appletsize_top)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        } 
     else if (y_pos < appletsize_bottom)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        } 
    
   
     //repaint applet
     repaint();

    try
    {
        // Stop thread for the speed
        Thread.sleep (10);
    }
    catch (InterruptedException ex)
    {
       
    }

        // set ThreadPriority to maximum value
        Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
    
}
}

//create an image off screen and loads it into the applet
public void update (Graphics g)
{
// initialize buffer
if (dbImage == null)
{
dbImage = createImage (this.getSize().width, this.getSize().height);
dbg = dbImage.getGraphics ();
}

// clear screen in background
dbg.setColor (getBackground ());
dbg.fillRect (0, 0, this.getSize().width, this.getSize().height);

// draw elements in background
dbg.setColor (getForeground());
paint (dbg);

// draw image on the screen
g.drawImage (dbImage, 0, 0, this);
}




/** paint - method allows you to paint into your applet. This method is called e.g. if you move your browser window or if you call repaint() */
public void paint (Graphics g) 

{ 
    // set color
    g.setColor (Color.red);

    // paint a filled colored circle
    g.fillOval (x_pos - radius, y_pos - radius, 2 * radius, 2 * radius);


}

// Method to handle mouse down events 
public boolean mouseDown (Event e, int x, int y) 
{
    // Change direction, put speed into a minus number 1 now become -1
    x_speed = - (x_speed); 
    return true;
}


}