Head First设计模式-装饰者模式-优快云博客

本文链接：https://blog.youkuaiyun.com/jltxgcy/article/details/12654199

本文介绍装饰者模式的应用场景及其实现方式，通过示例代码展示了如何动态为对象添加职责，而不使用子类实现。适用于希望扩展功能又不想修改现有代码的情况。

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一、整体代码

Beverage.java

public abstract class Beverage {
        String description = "Unknown Beverage";

        public String getDescription() {
                return description;
        }

        public abstract double cost();
}

CondimentDecorator.java

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

Espresso.java

public class Espresso extends Beverage {

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

        public double cost() {
                return 1.99;
        }
}

HouseBlend.java

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

        public double cost() {
                return .89;
        }
}

Mocha.java

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();
        }
}

StarbuzzCoffee.java

public class StarbuzzCoffee {

        public static void main(String args[]) {
                Beverage beverage = new Espresso();
                System.out.println(beverage.getDescription()
                                + " $" + beverage.cost());

                beverage = new Mocha(beverage);
                System.out.println(beverage.getDescription()
                                + " $" + beverage.cost());

                Beverage beverage1 = new HouseBlend();
                System.out.println(beverage1.getDescription()
                                + " $" + beverage1.cost());

                beverage1 = new Mocha(beverage1);
                System.out.println(beverage1.getDescription()
                                + " $" + beverage1.cost());
        }
}

二、结构图