import java.awt.*;
public class Ball
{
    int x, y, size, speed;
    int dirX, dirY;
    int appletWdt, appletHgt;
    public Ball( int _x, int _y, int _size, int _speed, int w, int h )
    {
        x = _x;		// (x, y) coordinates of ball
        y = _y;
        size = _size;	// width and height are same size
        speed = _speed;	// speed is number of pixels to move each time
        dirX = 1;		// direction is either +1 go right or -1 go left
        dirY = 1;		// direction is either +1 go down or -1 go up
        appletWdt = w;	// applet width
        appletHgt = h; 	// applet height
    }
    public void paint( Graphics g )			// called from applet
    {
        g.setColor( Color.BLUE );
        g.fillOval( x, y, size, size );
    }
    public void move( )
    {					 // move ball based on speed and direction
        x = x + speed * dirX;
        y = y + speed * dirY;
        if ( x < 0 )		  // hit left boundary, change direction
            dirX = 1;
        else if ( x > appletWdt )  // hit right boundary, change direction
            dirX = -1;
        if ( y < 0 )		  // hit top boundary, change direction
            dirY = 1;
        else if ( y > appletHgt )	  // hit bottom boundary, change direction
            dirY = -1;
    }
}