装饰者模式:动态的将责任附加到对象上。若要扩展功能,装饰者模式提供了比继承更有弹性的替代方案。
代码实现:
(1)先声明Beverage和CondimentDecorator两个抽象类
public abstract class Beverage {
String description = "Unknow Beverage";
public String getDescription(){
return description;
}
public abstract double cost();
}
public abstract class CondimentDecorator extends Beverage{
public abstract String getDescription();
}
(2)继承beverage和CondimentDecorator,实现相应的具体类
public class DarkRoast extends Beverage {
public DarkRoast() {
description = "Dark Roast";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return 1.20;
}
}
public class Decat extends Beverage{
public Decat() {
description = "Decat";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return 2.00;
}
}
public class Espresso extends Beverage{
public Espresso(){
description = "Espresso";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return 1.99;
}
}
public class HouseBlend extends Beverage{
public HouseBlend(){
description = "House Blend Coffee";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return .89;
}
}
public class Mocha extends CondimentDecorator{
Beverage beverage;
public Mocha(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
// TODO Auto-generated method stub
return beverage.getDescription() + ", Mocha";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return .20 + beverage.cost();
}
}
public class Soy extends CondimentDecorator{
Beverage beverage;
public Soy(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
// TODO Auto-generated method stub
return beverage.getDescription() + ", Soy";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return .15 + beverage.cost();
}
}
public class Whip extends CondimentDecorator {
Beverage beverage;
public Whip(Beverage beverage) {
this.beverage = beverage;
}
@Override
public String getDescription() {
// TODO Auto-generated method stub
return beverage.getDescription() + ", Whip";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return .25 + beverage.cost();
}
}
(3)测试代码
public class StarbuzzCoffee {
public static void main(String[] args) {
Beverage beverage = new Espresso();
System.out.println(beverage.getDescription() + " $" + beverage.cost());
Beverage beverage2 = new DarkRoast();
beverage2 = new Mocha(beverage2);
beverage2 = new Mocha(beverage2);
beverage2 = new Whip(beverage2);
System.out.println(beverage2.getDescription() + " $" + beverage2.cost());
}
}
测试结果:
Espresso $1.99
Dark Roast, Mocha, Mocha, Whip $1.8499999999999999