[关键字]:java,design pattern,设计模式,《Java与模式》学习,Strategy,策略模式,图书，折扣,DiscountStrategy [环境]:StarUML5.0 + JDK6 [作者]:Winty (wintys@gmail.com) [正文]:
package pattern.strategy; /** * 策略模式:Strategy Pattern * * 图书折扣的计算: * 1、无折扣 * 2、固定折扣(例如:提供10元的折扣) * 3、百分比折扣(例如:提供7%的折扣) * * @verison 2009-05-20 * @author Winty (wintys@gmail.com) * */ public class StrategyTest { public static void main(String[] args) { double discount = 0; Book book = new Book(88.5); book.setStrategy(new NoDiscountStrategy()); discount = book.getDiscount(); System.out.println("折扣:" + discount); book.setStrategy(new FlatDiscountStrategy(10)); discount = book.getDiscount(); System.out.println("折扣:" + discount); book.setStrategy(new PercentageDiscountStrategy(0.07)); discount = book.getDiscount(); System.out.println("折扣:" + discount); } } /** * 环境(Context) * @author Winty * */ class Book{ private double price; private DiscountStrategy strategy; public Book(double price){ this.price = price; } /** * 调用Strategy的策略方法进行计算 * @return 折扣数额 */ public double getDiscount(){ strategy.setPrice(price); return strategy.calculateDiscount(); } public DiscountStrategy getStrategy() { return strategy; } public void setStrategy(DiscountStrategy strategy) { this.strategy = strategy; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } } /** * 抽象策略:Strategy * @author Winty * */ abstract class DiscountStrategy{ private double price; public DiscountStrategy(){ } /** * 策略方法 * @return 折扣数额 */ public abstract double calculateDiscount(); public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } } /** * 具体策略:无折扣算法 * @author Winty * */ class NoDiscountStrategy extends DiscountStrategy{ public NoDiscountStrategy(){ } @Override public double calculateDiscount(){ return 0.0; } } /** * 具体策略：固定量折扣算法 * @author Winty * */ class FlatDiscountStrategy extends DiscountStrategy{ private double amount; public FlatDiscountStrategy(double amount){ this.amount = amount; } @Override public double calculateDiscount() { return amount; } public double getAmount() { return amount; } public void setAmount(double amount) { this.amount = amount; } } /** * 具体策略:百分比折扣策略 * @author Winty * */ class PercentageDiscountStrategy extends DiscountStrategy{ private double percent; public PercentageDiscountStrategy(double percent){ this.percent = percent; } @Override public double calculateDiscount() { return getPrice()*percent; } public double getPercent() { return percent; } public void setPercent(double percent) { this.percent = percent; } }原创作品，转载请注明出处。 作者:Winty (wintys@gmail.com) 博客:http://www.blogjava.net/wintys
