设计模式——装饰者模式

标签：设计模式

装饰者模式类图：

以下程序来自Head First设计模式中的实例代码，模拟了不同种类的饮料不同的售价计算方法。
 
1.定义饮料接口

package net.dp.decorator;
 
public abstract class Beverage {
    protected String description = "Unknown Beverage";
 
    public String getDescription() {
        return description;
    }
 
    public abstract double cost();
}

package net.dp.decorator.coffee;
 
import net.dp.decorator.Beverage;
 
public class Espresso extends Beverage {
 
    public Espresso() {
        description = "Espresso";
    }
 
    public double cost() {
        return 1.99;
    }
}

package net.dp.decorator;
 
public abstract class Beverage {
    protected String description = "Unknown Beverage";
 
    public String getDescription() {
        return description;
    }
 
    public abstract double cost();
}

package net.dp.decorator.coffee;
 
import net.dp.decorator.Beverage;
 
public class HouseBlend extends Beverage {
 
    public HouseBlend() {
        description = "House Blend Coffee";
    }
 
    public double cost() {
        return .89;
    }
}

package net.dp.decorator;
 
public abstract class CondimentDecorator extends Beverage {
    public abstract String getDescription();
}

package net.dp.decorator.flovoring;
 
import net.dp.decorator.Beverage;
import net.dp.decorator.CondimentDecorator;
 
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();
    }
}

package net.dp.decorator.flovoring;
 
import net.dp.decorator.Beverage;
import net.dp.decorator.CondimentDecorator;
 
public class Soy extends CondimentDecorator {
    Beverage beverage;
 
    public Soy(Beverage beverage) {
        this.beverage = beverage;
    }
 
    public String getDescription() {
        return beverage.getDescription() + ", Soy";
    }
 
    public double cost() {
        return .15 + beverage.cost();
    }
}

package net.dp.decorator.flovoring;
 
import net.dp.decorator.Beverage;
import net.dp.decorator.CondimentDecorator;
 
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();
    }
}

package net.dp.decorator;
 
import net.dp.decorator.coffee.DarkRoast;
import net.dp.decorator.coffee.Espresso;
import net.dp.decorator.coffee.HouseBlend;
import net.dp.decorator.flovoring.Mocha;
import net.dp.decorator.flovoring.Soy;
import net.dp.decorator.flovoring.Whip;
 
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 beverage3 = new HouseBlend();
        beverage3 = new Soy(beverage2);
        beverage3 = new Mocha(beverage2);
        beverage3 = new Whip(beverage2);
        System.out
                .println(beverage3.getDescription() + " $" + beverage3.cost());
    }
}

设计模式——装饰者模式

标签：设计模式

原文地址：http://blog.csdn.net/liuchangqing123/article/details/43938445