1. 定义

在不改变原有对象的基础上，将功能附加到对象上

2. 实现

基础：拍照功能

interface Component {
    void operation();
}
//拍照
class ConcreteComponent implements Component {
    @Override
    public void operation() {
        System.out.println("拍照.");
    }
}

定义装饰器

abstract class Decorator implements Component {
    Component component;
    public Decorator(Component component) {
        this.component = component;
    }
}

扩展美颜功能

//扩展美颜
class ConcreteDecorator1 extends Decorator {
    public ConcreteDecorator1(Component component) {
        super(component);
    }
    @Override
    public void operation() {
        System.out.println("添加美颜.");
        component.operation();
    }
}

扩展滤镜功能

//扩展滤镜
class ConcreteDecorator2 extends Decorator {
    public ConcreteDecorator2(Component component) {
        super(component);
    }
    @Override
    public void operation() {
        System.out.println("添加滤镜.");
        component.operation();
    }
}

使用

    public static void main(String[] args) {
        //拍照
        Component component = new ConcreteComponent();
        component.operation();
        //扩展美颜
        Component component1=new ConcreteDecorator1(component);
        component1.operation();
        //扩展滤镜
        Component component2=new ConcreteDecorator2(component1);
        component2.operation();
    }