Just one JCompnent is visible when a Panel (or JComponent) is added to another Panel using java

Question

I'm trying to add a JComponent to another using java, but just one of them (the top-level) is visible. I need to learn how to create nested panels. I need to learn how to paint what the panel has to show.

Here is my code:

import java.awt.*;

import javax.swing.*;



public class Main {
   public static void main(String[] a) {
      JFrame f = new JFrame();
      f.setTitle("window");
   f.setBounds(100,50,500,300);
   f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   MyComponent mc = new MyComponent(10, 10, 200, 200);
   MyComponent mc2 = new MyComponent(30, 30, 100, 100);
   mc.add(mc2);
   f.getContentPane().add(mc);
   f.setVisible(true);
}
static class MyComponent extends JComponent {

    private int swx;
    private int swy;
    private int nex;
    private int ney;

    public MyComponent(int swx, int swy, int nex, int ney){
        super();
        this.swx = swx;
        this.swy = swy;
        this.nex = nex;
        this.ney = ney;
    }

    public void paint(Graphics g){
        g.drawRect(swx, swy, nex, ney);
    }
}