Some doubts related to the use of the BorderLayout object

Some doubts related to the use of the BorderLayout object

I am studying Java Swing and I have a doubt related to the use of the
BorderLayout object.
I have this simple example program that create a ToolBar:
package com.andrea.menu;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
public class ToolBar extends JFrame {
public ToolBar() {
initUI();
}
public final void initUI() {
JMenuBar menubar = new JMenuBar(); // The menu bar containing
the main menu voices
JMenu file = new JMenu("File"); // Creo un menu a tendina
con etichetta "File" e lo aggiungo
menubar.add(file);
setJMenuBar(menubar); // Sets the menubar for
this frame.
JToolBar toolbar = new JToolBar();
ImageIcon icon = new ImageIcon(getClass().getResource("exit.png"));
JButton exitButton = new JButton(icon);
toolbar.add(exitButton);
exitButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
System.exit(0);
}
});
add(toolbar, BorderLayout.NORTH);
setTitle("Simple toolbar");
setSize(300, 200);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
ToolBar ex = new ToolBar();
ex.setVisible(true);
}
});
}
}
So it create a JToolBar object by the line:
JToolBar toolbar = new JToolBar();
and then it put it in the NORTH position of the BorderLayout object by the
line:
add(toolbar, BorderLayout.NORTH);
Reading the documentation I know that:
A border layout lays out a container, arranging and resizing its
components to fit in five regions: north, south, east, west, and center
My doubt is: the BorderLayout object whom it refers? At the external
JFrame container?
It means that it put the toolbar object in the NORTH position of my
JFrame? Or what?
Tnx
Andrea