Repaint() method calling in another class

I have a problem with repaint() method in my Java code. I want to call it in another class but I can't, something doesn't work at all. I've searched on forums, but nothing was able to help me out.

My Main class:

public class Main {

public static Main main;
public static JFrame f;
public Main(){

}

public static void main(String[] args) {
    main = new Main();

    f = new JFrame();
    Ball b = new Ball();

    f.getContentPane().setBackground(Color.GRAY);

    f.add(b);
    f.setSize(500, 500);
    f.setLocationRelativeTo(null);
    f.setTitle("Test");
    f.setVisible(true);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.addMouseMotionListener(b);
    f.addKeyListener(new Key());


}
}

Ball class where I created 2DGraphics for moving shapes:

public class Ball extends JLabel implements MouseMotionListener{

public Ball(){

}

public static double x = 10;
public static double y = 10;
public static double width = 40;
public static double height = 40;

String nick;
boolean isEllipse = true;

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

    Graphics2D g2d = (Graphics2D) g;
    if(isEllipse){
        Ellipse2D e2d = new Ellipse2D.Double(x, y, width, height);  
        g2d.setColor(Color.RED);
        g2d.fill(e2d);
    }
    else{
        Rectangle2D r2d = new Rectangle2D.Double(x, y, width, height);
        g2d.setColor(Color.GREEN);
        g2d.fill(r2d);
    }

}

@Override
public void mouseDragged(MouseEvent e) {
    isEllipse = false;
    x = e.getX() - 30;
    y = e.getY() - 40;
    this.repaint(); 
}

@Override
public void mouseMoved(MouseEvent e) {
    x = e.getX() - 30;
    y = e.getY() - 40;
    isEllipse = true;
    this.repaint();
}
}

And Key class where I put KeyListener for move the shapes by key pressing:

public class Key extends Ball implements KeyListener {

public Key() {
}

@SuppressWarnings("static-access")
@Override
public void keyPressed(KeyEvent e) {

    if(e.getKeyCode() == KeyEvent.VK_W){
        super.x += 10;
        super.repaint();
        System.out.println("x: " + super.x);
    }
}

@Override
public void keyReleased(KeyEvent e) {
    // TODO Auto-generated method stub

}

@Override
public void keyTyped(KeyEvent e) {
    // TODO Auto-generated method stub

}
}

But something is wrong with this code: super method doesn't work for Key class. Everything in Ball class is working well. Where is the problem?