import java.awt.Panel;                                        // ***

public class BoundedBall extends MovableBall
{
    private Panel myWorld;                                     // ***

    public BoundedBall( int x, int y, int r,
                        double dx, double dy, Panel aWorld )   // ***
    {
        super( x, y, r, dx, dy );
        myWorld = aWorld;
    }

    public void move()
    {
        super.move();

        int maxHeight = myWorld.getHeight();
        int maxWidth  = myWorld.getWidth();

        if ( (x() < 0) || (x() > maxWidth) )
            setMotion( -xMotion(), yMotion() );
        if ( (y() < 0) || (y() > maxHeight) )
            setMotion( xMotion(), -yMotion() );
    }
}