Callbacks, and using interfaces as arguments

I have the following code snippets. Both has a method call to
addWindowListener

It is my understanding that BookOrderFrame is using a callback method
to implement the interface for WindowListener. Am I correct?

LoanCalculatorFrame otoh, does it substantially different and does not
even state "implements WindowListener".

So can anyone please explain what LoanCalculatorFrame does and whether
and how it is better/worse than what BookOrderFrame is doing?

Thanks.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.*;


public class LoanCalculatorFrame extends JFrame
{
public LoanCalculatorFrame()
{
setTitle("Loan Calculator");
Toolkit tk = Toolkit.getDefaultToolkit();
Dimension d = tk.getScreenSize();
System.out.println("Screen:" + d.width + " by " + d.height + "
pixels");
int height = 200;
int width = 267;
setBounds((d.width-width)/2, (d.height-height)/2, width, height);
setResizable(false);
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
}
);
Container contentPane = getContentPane();
JPanel panel = new JPanel();
contentPane.add(panel);

}
}



import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.*;

public class BookOrderFrame extends JFrame implements WindowListener
{
public BookOrderFrame()
{
setTitle("Book Order");
setBounds(267, 200, 267, 200);
addWindowListener(this);
}

public void windowDeactivated(WindowEvent e)
{
}

public void windowActivated(WindowEvent e)
{
}

public void windowDeiconified(WindowEvent e)
{
}

public void windowIconified(WindowEvent e)
{
}

public void windowClosed(WindowEvent e)
{
}

public void windowClosing(WindowEvent e)
{
System.exit(0);
}

public void windowOpened(WindowEvent e)
{
}
}

.