步骤 1

创建一个接口：

 public interface Shape {
       void draw();
 }

步骤 2

创建实现接口的实体类。

• Rectangle.java

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

• Circle.java

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

步骤 3

创建实现了 Shape 接口的抽象装饰类。

• ShapeDecorator.java

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

步骤 4

创建扩展了 ShapeDecorator 类的实体装饰类。

• RedShapeDecorator.java

   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");
       }
  }
  

步骤 5

使用 RedShapeDecorator 来装饰 Shape 对象。

• DecoratorPatternDemo.java

   public class DecoratorPatternDemo {
       public static void main(String[] args) {
  
          Shape circle = new Circle();
  
          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();
        }
  }
  

步骤 6

执行程序，输出结果：

    Circle with normal border
    Shape: Circle
   ------------------------------------------
    Circle of red border
    Shape: Circle
    Border Color: Red
   ------------------------------------------
    Rectangle of red border    
    Shape: Rectangle
     Border Color: Red