Problème bouton

 import java.awt.Panel;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Main {

 public static void main(String[] args) {
  
  JFrame frame = new JFrame ();
  Ecran Ecran = new Ecran();
  frame.setVisible(true);
  frame.setSize(800, 500);
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.setLocationRelativeTo(null);
  frame.add(new Ecran ());
  
        
 }
}

import java.awt.Graphics;

import javax.swing.JButton;
import javax.swing.JPanel;



public class Ecran extends JPanel {
 

 public  Ecran () {
 JButton button = new JButton ("je suis un bouton");
 button.setBounds(88, 88, 88, 88);
    button.setVisible(true);
 add(button);
 
 }
 
 public void paintComponent (Graphics g) {
  
  
 }
 

}