JAVA: Uma animação Simples

package animacaosimples;
import javax.swing.*;
import java.awt.*;

public class AnimacaoSimples {
        int x = 70;
        int y = 70;

    public static void main(String[] args) throws InterruptedException{
        AnimacaoSimples sistema = new AnimacaoSimples();
        sistema.mostrar();

    }
    public void mostrar() throws InterruptedException{
        JFrame janela = new JFrame();
        janela.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Painel desenharPainel = new Painel();

        janela.getContentPane().add(desenharPainel);
        janela.setSize(300,300);
        janela.setVisible(true);

        for (int i = 0; i < 500; i ++){
            x++;

            desenharPainel.repaint();

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

        }
    }

    public class Painel extends JPanel {
        @Override
        public void paintComponent(Graphics g){
            g.setColor(Color.white);
            g.fillRect(0, 0, this.getWidth(), this.getHeight());

            for(int i = 0; i < 10 ; i++){
                g.setColor(Color.red);
                g.fillOval(x+(i*30), y*2, 20, 20);
                g.setColor(Color.blue);
                g.fillOval(x+(i*30), 30+y*2, 20, 20);
            }

    }
}

}