public class Anim extends JPanel implements Runnable {

    Pilka P1;
    boolean going = true;

    Thread animator;
    Pilka P2;
    double deltaX;
    double deltaY;
    double distance;

    public Anim() {
        P1 = new Pilka(50, 80, 40, Color.green);
        P1.setX(50);
        P1.setY(80);
        P1.setxSpeed(4);
        P1.setySpeed(2);

        P2 = new Pilka(50, 80, 70, Color.green);
        P2.setX(150);
        P2.setY(80);
        P2.setxSpeed(4);
        P2.setySpeed(2);



        animator = new Thread(this);
        animator.start();

    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        P1.draw(g);
        P2.draw(g);
        g.setColor(Color.green);



        // draw center of circle
        g.fillOval((int) P1.getX() - 5, (int) P1.getY() - 5, 10, 10);
        g.fillOval((int) P2.getX() - 5, (int) P2.getY() - 5, 10, 10);

    }

    @Override
    public void run() {
        while (going) {
            P1.move();
            P2.move();

            checkCollision();

            repaint();

            try {
                Thread.sleep(20);
            } catch (InterruptedException ex) {
            }
        }
    }

    public void checkCollision() {

        deltaX = Math.abs(P1.getX() - P2.getX());
        deltaY = Math.abs(P1.getY() - P2.getY());
        distance = deltaX * deltaX + deltaY * deltaY;

        if (distance < (P1.getDiametar() / 2 + P2.getDiametar() / 2) * (P1.getDiametar() / 2 + P2.getDiametar() / 2)) {

            double newxSpeed1 = (P1.getxSpeed() * (4 - 7) + (2 * 7 * P2.getxSpeed())) / 11;

            double newxSpeed2 = (P2.getxSpeed() * (7 - 4) + (2 * 4 * P1.getxSpeed())) / 11;

            double newySpeed1 = (P1.getySpeed() * (4 - 7) + (2 * 7 * P2.getySpeed())) / 11;

            double newySpeed2 = (P2.getySpeed() * (7 - 4) + (2 * 4 * P1.getySpeed())) / 11;

            P2.setxSpeed(newxSpeed2);
            P2.setySpeed(newySpeed2);
            P1.setxSpeed(newxSpeed1);
            P1.setySpeed(newySpeed1);

        }
    }

}