paint only paints one obj

I'm just starting Java Swing and I want to create circles so I have a class that draws only circles and a constructor to set size and starting point, then in main, I create a new JFrame and add this obj. It's working, but when I try to add more circle objs to my JFrame, it doesn't show up. I know it's trivial...

Code :

import javax.swing.*;
import java.awt.*;
 
public class Circle extends JPanel
{
  private int starting_x;
  private int starting_y;
  private int width;
  private int height;
 
   public Circle(int x, int y,int w, int h)
   {
      this.starting_x = x;
      this.starting_y = y;
      this.width = w;
      this.height = h;
   }
 
  public void paintComponent(Graphics g)
  {
	super.paintComponent(g);
 
	Graphics2D g2d = (Graphics2D) g;
 
	g2d.setColor(Color.black);
	g2d.fillOval(start_x-1, start_y-1, width+2, height+2);
 
   }
}

Code :

//main in another file
import javax.swing.*;
 
public class Runner
{
   public static void main(String[] args)
   {
      JFrame f = new JFrame();
      f.add( new Circle(100,100,34,34) );//this shows
      f.add( new Circle(300,305,34,34) );//this doesn't show though
      f.setVisible(true);
      f.setSize(1000,1000);  
   }
}