Strategy - Design Patterns Java - page 188

CHALLENGE 23.2
Fill in the class diagram in Figure 23.3, which shows the recommendation logic
refactored into a collection of strategy classes.
Figure 23.3. Complete this diagram to show a refactoring of the recommendation
software, with strategies appearing as implementations of a common interface.
Each implementation of the Advisor interface should supply a singleton that offers
the recommend() operation. You might correspondingly give each class a single, private
constructor to prevent other classes from instantiating it.
The constructor for PromotionAdvisor should investigate whether a promotion is on. You
might then supply this class with a hasItem() method that indicates whether there is
a promoted item.
package com.oozinoz.recommend;
import java.io.*;
import java.util.*;
import com.oozinoz.fireworks.*;
public class PromotionAdvisor implements Advisor
{
public static final PromotionAdvisor singleton =
new PromotionAdvisor();
private Firework promoted;
private PromotionAdvisor()
{
try
{
Properties p = new Properties();
p.load(
ClassLoader.getSystemResourceAsStream(
"config/strategy.dat"));