装饰者模式学习

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装饰者模式学习，记录下来以后看，图和代码都和书上的一模一样。

代码片段1：（饮料抽象类）

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

代码片段2：（抽象装饰者）

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

代码片段3：（具体的饮料）

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

代码片段4：（具体的饮料）

public class HouseBlend extends Beverage {    public HouseBlend(){        description = "HouseBlend";    }    @Override    public double cost() {        return 0.89;    }}

代码片段5：（具体的装饰者）

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 0.2 +beverage.cost();    }}

代码片段6：（具体的装饰者）

public class Soy extends CondimentDecorator {    Beverage beverage;    public Soy(Beverage beverage){        this.beverage = beverage;    }    @Override    public String getDescription() {        return beverage.getDescription() + " ,Soy";    }    @Override    public double cost() {        return 0.5 + beverage.cost();    }}

测试代码：

Beverage beverage3 = new HouseBlend();beverage3 = new Mocha(beverage3);beverage3 = new Soy(beverage3);  System.out.println(beverage3.getDescription() + " $ " +beverage3.cost());

运行结果：
HouseBlend，Mocha, Soy $ 1.59

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