Mouse movement delays repaint()

Question

I've been coding a project of balls bouncing of the wall and everything works fine besides when I move the mouse over the drawing panel fast enough, the repaint is laggy. So I made an example in Edit 2 and the problem exists there too. Why? How can I fix it or work around it?

Edit 1: This is how my code looks like: here
Edit 2: I created this example to make it more clear.

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

import static javax.swing.JFrame.EXIT_ON_CLOSE;

public class DrawingPanel extends JPanel
{
    public Ball ball;
    public DrawingPanel()
    {
        super();
        setPreferredSize(new Dimension(300, 100));
        setBackground(Color.black);
        this.ball = new Ball(10);
        this.ball.start();
    }
    public static void main(String[] args)
    {
        JFrame frame = new JFrame("Laggy ball");
        DrawingPanel panel = new DrawingPanel();
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.add(panel);
        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
        while(true)
        {
            try
            {
                Thread.sleep(17);
            } catch (InterruptedException e)
            {
                e.printStackTrace();
            }
            panel.repaint();
        }
    }

    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        ball.draw(g);
    }

    public class Ball extends Thread
    {
        public int position;
        public int velocity;
        public Ball(int velocity)
        {
            super();
            this.position = 0;
            this.velocity = velocity;
        }
        void draw(Graphics g)
        {
            g.setColor(Color.blue);
            g.fillOval(position, 50, 20, 20);
        }
        void update()
        {
            position += velocity;
            if(position > getWidth() || position < 0)
                velocity *= -1;
        }
        @Override
        public void run()
        {
            while(true)
            {
                try
                {
                    Thread.sleep(17);
                } catch (InterruptedException e)
                {
                    e.printStackTrace();
                }
                update();
            }
        }
    }
}

Edit 3: One problem solved. At least I know the problem is not the code but my laptop.

Edit 4: I noticed the problem only exists while using external mouse. Otherwise it's all fine. It was a local problem not with the code. Thanks for help, though!