Slight problem with threads....

Question

Hello,
Just started learning threads a few days ago.. my objective is to move an oval from left to right, then right to left, back and forth and so on.. however, it wont work, the source code i have below seems logical, but it doesnt fulfill my objective..
// The "MovingCircleUsingThreads" class.
import java.applet.*;
import java.awt.*;
public class MovingCircleUsingThreads extends Applet implements Runnable
    int x = 0;
    Thread t;
    public void init ()
        t = new Thread (this);
        t.start ();
    } // init method
    public void run ()
        try
            while (true)
                repaint ();
                Thread.sleep (20);
        catch (Exception e)
    public void paint (Graphics g)
        int speed = 10;
        Dimension d = getSize ();
        g.fillOval (x, d.height / 4, 50, 50);
        x = x + speed;
        if (x + 50 == d.width)
            speed = -10;
} // MovingCircleUsingThreads classI think the paint method is wrong, but it all seems logical.. x starts off in the left side, moves to the right side by 10, when x + 50 == d.width, the oval is at the right edge, and speed = -10, so it should be moving to the left by 10, but instead, the oval disappears.. :( can anyone help?
public void paint (Graphics g)
        int speed = 10;
        Dimension d = getSize ();
        g.fillOval (x, d.height / 4, 50, 50);
        x = x + speed;
        if (x + 50 == d.width)
            speed = -10;
    }

Answer 1

public void paint (Graphics g)
int speed = 10;
Dimension d = getSize ();
g.fillOval (x, d.height / 4, 50, 50);
x = x + speed;
if (x + 50 == d.width)
speed = -10;
}So you are setting speed to -10, and then you are
leaving paint?
Can not see this having any impact on processing...Im setting speed to -10 because I want the oval to go left.... But it wont, after the oval goes from left to right, it disappears..
Try changing the following:
if (x + 50 == d.width)
speed = -10;to
if (x + 50 >= d.width)
speed = -10;
Tried changing that before, oval disappears after it goes to right side :\