设计模式（装饰模式）

装饰模式用于给对象动态而灵活的添加属性，主要包含如下几个角色：

• Component：定义一个对象接口，可以给这些对象动态地添加职责，本例中是Product
• ConcreteComponent:具体的对象，用以被添加属性，本例中是ProductImpl,通过addAttribute被添加属性
• Decorator：装饰器的抽象，维持一个Component指针，并继承该指针；本例中是BaseChange
• ConcreteComponent:具体的装饰器，本例中是OneChange和TwoChange

代码如下：

• Product

public interface Product {
    public void addAttribute();
}

• ProductImpl

public class ProductImpl implements Product {

    @Override
    public void addAttribute() {
        System.out.println("Add base Attribute");
    }
}

• BaseChange

public class BaseChange implements Product {
    
    private Product product;
    
    public BaseChange(Product product){
        this.product = product;
    }

    @Override
    public void addAttribute() {
        product.addAttribute();
    }
}

• OneChange && TwoChange

public class OneChange extends BaseChange {

    public OneChange(Product product) {
        super(product);
    }
    
    @Override
    public void addAttribute() {
        super.addAttribute();
        System.out.println("One Change");
    }
}

public class TwoChange extends BaseChange {
    
    public TwoChange(Product product) {
        super(product);
    }
    
    @Override
    public void addAttribute() {
        super.addAttribute();
        System.out.println("Two Change");
    }
}

• App

public class App {

    public static void main(String[] args) {
        Product product = new ProductImpl();
        
        Product change = new TwoChange(new OneChange(product));
        change.addAttribute();
    }

}

输出结果为：

Add base Attribute
One Change
Two Change