装饰器模式

装饰器模式

这种模式创建了一个装饰类，用来包装原有的类，并在保持类方法签名完整性的前提下，提供了额外的功能。

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1、创建一个抽象类

public interface Shape {
    void draw();
}

2、编写抽象类的实现类

public class Circle implements Shape {
    @Override
    public void draw() {
        System.out.println("Circle");
    }
}

public class Rectangle implements Shape {
    @Override
    public void draw() {
        System.out.println("Rectangle");
    }
}

3、创建实现了 Shape 接口的抽象装饰类

public abstract class ShapeDecorator  implements  Shape{
    protected Shape decoratedShape;

    public ShapeDecorator (Shape decoratedShape){
        this.decoratedShape = decoratedShape;
    }

    public void draw(){
        decoratedShape.draw();
    }
}

4、实现抽象装饰类

public class ReadShapeDecorator extends  ShapeDecorator {
    public ReadShapeDecorator(Shape decoratedShape) {
        super(decoratedShape);
    }
    public  void draw(){
        decoratedShape.draw();
        setRedBorder(decoratedShape);
    }

    private void setRedBorder(Shape decoratedShape) {
        System.out.println("Border Color: Red");
    }

}

5、测试类

public class DecoratorPatternDemo {
    public static void main(String[] args) {
        Shape circle = new Circle();
        ShapeDecorator readCircle = new ReadShapeDecorator(new Circle());
        ShapeDecorator redRectangle = new ReadShapeDecorator(new Rectangle());
        circle.draw();
        readCircle.draw();
        redRectangle.draw();
    }
}

6、测试结果

Circle
Circle
Border Color: Red
Rectangle
Border Color: Red

 转载 ：https://www.runoob.com/design-pattern/decorator-pattern.html