Design Patterns Java™ Workbook

Chapter 21. Template Method

Figure 21.1. The sort() method can sort any list, using a method that you supply to

perform the comparison step of the algorithm.

The static sort() method accepts a list and an instance of Comparator. The Comparator
interface requires its implementer to supply the comparison step of the sorting algorithm.
The compare() method must return a number less than, equal to, or greater than 0. These
values correspond to the idea that, in a sense that you define, object o1 is less than, equal to,
or greater than object o2. For example, you might implement compare() to compare
the sharpness of two rocks or the apogee of two rockets.

The following class sorts a collection of rockets by their apogees:

package com.oozinoz.applications;
import java.util.;
import com.oozinoz.units.;
import com.oozinoz.fireworks.*;
public class ShowComparator implements UnitConstants
{
public static void main(String[] args)
{
Rocket r1 = new Rocket(
"Mach-it", 22.95, (Length) METER.times(1000));