设计模式读书笔记-3装饰模式Decorator

1.定义
动态地给一个对象添加一些额外的职责，就增加功能来说，装饰模式比生成子类更为灵活。

2.类图


3.实例



StarbuzzCoffee

package headfirst.decorator.starbuzz;

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());
	}
}

Beverage

package headfirst.decorator.starbuzz;

public abstract class Beverage {
	String description = "Unknown Beverage";
  
	public String getDescription() {
		return description;
	}
 
	public abstract double cost();
}

DarkRoast

package headfirst.decorator.starbuzz;

public class DarkRoast extends Beverage {
	public DarkRoast() {
		description = "Dark Roast Coffee";
	}
 
	public double cost() {
		return .99;
	}
}

Espresso

package headfirst.decorator.starbuzz;

public class Espresso extends Beverage {
  
	public Espresso() {
		description = "Espresso";
	}
  
	public double cost() {
		return 1.99;
	}
}

CondimentDecorator

package headfirst.decorator.starbuzz;

public abstract class CondimentDecorator extends Beverage {
	public abstract String getDescription();
}

Mocha

package headfirst.decorator.starbuzz;

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 .20 + beverage.cost();
	}
}

Whip

package headfirst.decorator.starbuzz;
 
public class Whip extends CondimentDecorator {
	Beverage beverage;
 
	public Whip(Beverage beverage) {
		this.beverage = beverage;
	}
 
	public String getDescription() {
		return beverage.getDescription() + ", Whip";
	}
 
	public double cost() {
		return .10 + beverage.cost();
	}
}