Java: Example - Kilometers to Miles - User Interface Only

// intro-window/KmToMilesNoModel.java - Input field, button, output field
//    This is the user interface for the Km to Mi conversion.
//    The button does nothing in this program.
//    Fred Swartz, 2004-10-28

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

///////////////////////////////////////////////// class KmToMilesNoModel
class KmToMilesNoModel {
    //====================================================== method main
    public static void main(String[] args) {
        JFrame window = new KmToMilesGUI();
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setVisible(true);
    }
}


///////////////////////////////////////////////////// class KmToMilesGUI
class KmToMilesGUI extends JFrame {
    //======================================= instance variables //Note 1
    private JTextField m_milesTf      = new JTextField(10);      //Note 2
    private JTextField m_kilometersTf = new JTextField(10);
    private JButton    m_convertBtn   = new JButton("Convert");  //Note 3


    //====================================================== constructor
    public KmToMilesGUI() {
        //... Create content panel, set layout, add components
        JPanel content = new JPanel();                           //Note 4
        content.setLayout(new FlowLayout());   // use FlowLayout //Note 5
        content.add(new JLabel("Kilometers")); // create, add label //Note 6
        content.add(m_kilometersTf);           // add input field
        content.add(m_convertBtn);             // add button
        content.add(new JLabel("Miles"));      // create, add label
        content.add(m_milesTf);                // add output field
        this.setContentPane(content);                            //Note 7
        this.pack();                                             //Note 8
        
        //... Set window characteristics
        this.setTitle("Kilometers to Miles");
    }//end constructor
}//end class KmToMilesGUI