Head First 裝飾者模式

 

1、類圖

 

2、示例代碼

      類圖：

　　

 

 

 　　代碼：

            一、飲料類

     　　

/**
 * 飲料類
 */
public abstract class Beverage {

    public String  description = "Unknown Beverage";

    public String getDescription(){
        return description;
    }

    public abstract double cost();

}

　　

　　二、具體飲料類

public class Espresso extends Beverage {

    public Espresso() {
        description = "Espresso";
    }

    @Override
    public double cost() {
        return 1.99;
    }
}


public class HouseBlend extends Beverage {

    public HouseBlend() {
        description = "House Blend Coffee";
    }

    @Override
    public double cost() {
        return 0.89;
    }
}

　　

　　三、調料 類，必須讓CondimentDecorator可以取代Beverage，因此將CondimentDecorator擴展自Beverage

/**
 * 調料類
 */
public abstract class CondimentDecorator extends Beverage{

    public abstract String  getDescription();

}

 

　　四、具體調料類

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();
    }
}



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 0.3 + beverage.cost();
    }
    
}



public class Whip extends CondimentDecorator {

    Beverage beverage;

    public Whip(Beverage beverage) {
        this.beverage = beverage;
    }

    @Override
    public String getDescription() {
        return beverage.getDescription() + ", Whip";
    }

    @Override
    public double cost() {
        return 0.4 + beverage.cost();
    }
}

　　五、訂單測試類

/**
 * 咖啡供應類
 */

public class StarbuzzCoffee {

    public static void main(String[] args) {

        //訂一杯Espresso，不須要調料
        Beverage beverage = new Espresso();
        System.out.println(beverage.getDescription() + " $" + beverage.cost());

        //來一杯調料爲豆漿、摩卡、奶泡的HouseBlend咖啡
        Beverage beverage1 = new HouseBlend();
        beverage1 = new Soy(beverage1);
        beverage1 = new Mocha(beverage1);
        beverage1 = new Whip(beverage1);
        System.out.println(beverage1.getDescription() + " $" + beverage1.cost());
    }
}

 

3、使用場景

　　須要擴展一個類的功能，或給一個類增長附加功能。

　　須要動態地給一個對象增長功能，這些功能能夠再動態地撤銷。

　　須要爲一批的兄弟類進行改裝或加裝功能，固然是首選裝飾模式。