本文介绍了一种遵循开闭原则的设计模式——装饰者模式。装饰者模式允许在不修改原有类的前提下增加新的功能，通过继承装饰者基类并实现在运行时动态地为对象附加职责来实现。文中提供了饮料类作为示例，展示了如何使用装饰者模式来扩展其功能。
Design Principle(Open-Closed Principle)
- Classes should be open for extension, but closed for modification.
The Decorator Pattern attaches additional responsibilitis to an object dynamically.
Decorator provide a flexible alternative to subclassing for extending functionality.
public abstract class Beverage{
String description = "unknown Beverage";
public String getDescription(){
return description;
}
public abstract double cost();
}
public abstract class CondimentDecorator extends Beverage{
public abstract String getDescription();
}
public class Espresso extends Beverage{
public Espresso(){
description = "Espresso";
}
public double cost(){
return 1.99;
}
}
public class HouseBlend extends Beverage{
public HouseBlend(){
description = "House Blend Coffee";
}
public double cost(){
return 0.89;
}
}
public class Mocha extends CondimentDecorator{
Beverage beverage;
public Mocha(Beverage beverage){
this.beverage = beverage;
}
public String getDescription(){
return beverage.getDescription +", Mocha";
}
public double cost(){
return 0.20 + beverage.cost();
}
}
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