一起来学设计模式之装饰器模式

// 定义一个基本的组件接口
interface Component {
    void operation();
}
// 定义一个具体的组件类
class ConcreteComponent implements Component {
    public void operation() {
        System.out.println("ConcreteComponent.operation()");
    }
}
// 定义一个装饰器基类，维护一个指向被装饰对象的引用
class Decorator implements Component {
    private Component component;
    public Decorator(Component component) {
        this.component = component;
    }
    public void operation() {
        component.operation();
    }
}
// 定义一个具体的装饰器类，实现了基础功能的扩展
class ConcreteDecorator extends Decorator {
    public ConcreteDecorator(Component component) {
        super(component);
    }
    public void operation() {
        super.operation();
        System.out.println("ConcreteDecorator.operation()");
    }
}
// 使用示例
public class DecoratorDemo {
    public static void main(String[] args) {
        Component component = new ConcreteComponent();
        Component decorator = new ConcreteDecorator(component);
        decorator.operation();
    }
}

// 基础商品类
public class Product {
    private String name;
    private double price;
    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }
    public String getName() {
        return name;
    }
    public double getPrice() {
        return price;
    }
}
// 装饰器基类
public class ProductDecorator extends Product {
    protected Product product;
    public ProductDecorator(Product product) {
        super(product.getName(), product.getPrice());
        this.product = product;
    }
    @Override
    public String getName() {
        return product.getName();
    }
    @Override
    public double getPrice() {
        return product.getPrice();
    }
}
// 礼品包装装饰器
public class GiftWrapDecorator extends ProductDecorator {
    private static final double GIFT_WRAP_PRICE = 5.0;
    public GiftWrapDecorator(Product product) {
        super(product);
    }
    @Override
    public String getName() {
        return super.getName() + " (gift wrap)";
    }
    @Override
    public double getPrice() {
        return super.getPrice() + GIFT_WRAP_PRICE;
    }
}
// 定制化贺卡装饰器
public class GreetingCardDecorator extends ProductDecorator {
    private static final double GREETING_CARD_PRICE = 3.0;
    private String message;
    public GreetingCardDecorator(Product product, String message) {
        super(product);
        this.message = message;
    }
    @Override
    public String getName() {
        return super.getName() + " (with greeting card)";
    }
    @Override
    public double getPrice() {
        return super.getPrice() + GREETING_CARD_PRICE;
    }
    public String getMessage() {
        return message;
    }
}