Something

import java.awt.*;import javax.swing.*;  public class Boll extends JPanel implements Runnable {          private Thread aktivitet;        private int r, x0, y0, x0old, y0old;        private int xSteg, ySteg;        private boolean bollaktivitet = false;        private String färg;            public Boll (int radie, int xHast, int yHast, String färg) {                r = radie; xSteg = xHast; ySteg = yHast;                x0 = r; y0 = r;                x0old = x0; y0old = y0;                färg = färg;          }            public void start() {                 if (aktivitet ==null) {                        aktivitet = new Thread(this);                 }                aktivitet.start();          }         public void stop() {                if (aktivitet != null) {                        aktivitet.interrupt();                        aktivitet = null;                 }        }         public void paint (Graphics g) {            g.setColor(Color.white);                        g.fillOval(x0old - r, y0old -r, 2*r, 2*r);        	g.setColor(Color.blue);                       g.fillOval(x0-r, y0-r, 2*r, 2*r);         }         public void run () {                while (!aktivitet.isInterrupted()) {                        try {                        		aktivitet.sleep(50);                        		x0old = x0;                        		if (x0-r+xSteg < 0 || x0+r+xSteg > getSize().width)                                        xSteg = -xSteg;                                x0 += xSteg;                                 y0old = y0;                                if (y0-r+ySteg < 0 || y0+r+ySteg > getSize().height)                                        ySteg = -ySteg;                                y0 += ySteg;                                repaint();                        } catch (InterruptedException ne) {                                System.out.println ("");                        }                }        } }