Java JFrame content pane with null layout manager

import java.awt.Container;

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

public class Main {
  public static void main(String[] args) {
    JFrame frame = new JFrame("Adding Components to JFrame");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container contentPane = frame.getContentPane();
    // Add a Close button
    //ww  w .j a v a  2s .c  o  m
    contentPane.setLayout(null);
    
    JButton closeButton = new JButton("Close");
    contentPane.add(closeButton);

    closeButton.setBounds(10, 10, 30, 30); 

    frame.setSize(200,200);
    frame.setVisible(true);
  }
}