Java: Kilometer to Miles - Formatted

// KmToMiles.java --  Converts kilometers to miles.
// Michael Maus, 9 Sept 2004
//
// Note: Formats the miles to one decimal place.

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

public class KmToMilesFormatted {
    
    public static void main(String[] args) {
        //... Constants
        final double MILES_PER_KILOMETER = 0.621;
        final DecimalFormat ONE_DECIMAL_PLACE = new DecimalFormat("0.0");
        
        //... Variables
        String kmStr;       // String version of km before conversion to double.
        double kilometers;  // Number of kilometers.
        double miles;       // Number of miles.
        String milesStr;    // String version of miles after formatting.
        
        //... Input
        kmStr = JOptionPane.showInputDialog(null, "Enter number of kilometers.");
        kilometers = Double.parseDouble(kmStr);
        
        //... Computation
        miles = kilometers * MILES_PER_KILOMETER;
        
        //... Output
        milesStr = ONE_DECIMAL_PLACE.format(miles);
        JOptionPane.showMessageDialog(null, kilometers + " kilometers is " 
                                          + milesStr + " miles.");
        
        //... Stop
        System.exit(0);  // Stop GUI program
    }
}