装饰器模式

装饰器模式

本质是继承了父类的新的装饰类,重写了父类的方法,前后各扩展功能,中间调用super父类方法
1.设计抽象类实现接口

public abstract class ShapeDecorator implements Shape {
   protected Shape decoratedShape;
 
   public ShapeDecorator(Shape decoratedShape){
      this.decoratedShape = decoratedShape;
   }
 
   public void draw(){
      decoratedShape.draw();
   }  
}

2.创建装饰类继承抽象类,并重写相关接口方法

public class RedShapeDecorator extends ShapeDecorator {
 
   public RedShapeDecorator(Shape decoratedShape) {
      super(decoratedShape);     
   }
 
   @Override
   public void draw() {
      decoratedShape.draw();         
      setRedBorder(decoratedShape);
   }
 
   private void setRedBorder(Shape decoratedShape){
      System.out.println("Border Color: Red");
   }
}

3.使用多态特性,定义变量的接受类型

public class DecoratorPatternDemo {
   public static void main(String[] args) {
      // Circle ,Rectangle是实现了Shape接口的实现类
      Shape circle = new Circle();
      ShapeDecorator redCircle = new RedShapeDecorator(new Circle());
      ShapeDecorator redRectangle = new RedShapeDecorator(new Rectangle());
      //Shape redCircle = new RedShapeDecorator(new Circle());
      //Shape redRectangle = new RedShapeDecorator(new Rectangle());
      System.out.println("Circle with normal border");
      circle.draw();
 
      System.out.println("\nCircle of red border");
      redCircle.draw();
 
      System.out.println("\nRectangle of red border");
      redRectangle.draw();
   }
}

结果

Circle with normal border
Shape: Circle

Circle of red border
Shape: Circle
Border Color: Red

Rectangle of red border
Shape: Rectangle
Border Color: Red