装饰者模式动态地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方案
容易引入大量小类
/**
* 饮料
* @author huangy on 2019-05-19
*/
public abstract class Beverage {
String description = "Unknown Beverage";
public String getDescription() {
return description;
}
public abstract double cost();
}
/**
* 调料(装饰者抽象类)
* @author huangy on 2019-05-19
*/
public abstract class CondimentDecorator extends Beverage {
public abstract String getDescription();
}
/**
* 浓缩咖啡
* @author huangy on 2019-05-19
*/
public class Espresso extends Beverage {
public Espresso() {
description = "Espresso";
}
@Override
public double cost() {
return 1.99;
}
}
/**
* @author huangy on 2019-05-19
*/
public class Mocha extends CondimentDecorator {
Beverage beverage;
public Mocha(Beverage beverage) {
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ", Mocha";
}
@Override
public double cost() {
return 0.20 + beverage.cost();
}
}
public class StarbuzzCoffee {
public static void main(String[] args) {
Beverage beverage = new Espresso();
Mocha mocha = new Mocha(beverage);
System.out.println(mocha.getDescription());
System.out.println(mocha.cost());
}
}