.idea/misc.xml

+<?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
   <component name="FrameworkDetectionExcludesConfiguration">
     <file type="web" url="file://$PROJECT_DIR$" />
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" project-jdk-name="corretto-16" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" project-jdk-name="11" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file

src/main/java/shape/AbstractShape.java

+package shape;
+
+abstract public class AbstractShape implements Shape {
+
+
+}

src/main/java/shape/Decorator.java

+package shape;
+
+abstract public class Decorator implements Shape{
+    private Shape decoratedShape;
+
+    Decorator(){
+
+    }
+}

src/main/java/shape/Rectangle.java

@@ -4,7 +4,7 @@ import javafx.geometry.Point2D;
 import javafx.scene.canvas.GraphicsContext;
 import javafx.scene.paint.Color;
 
-public class Rectangle implements Shape{
+public class Rectangle extends AbstractShape{
     Color color;
     Rectangle(Color color, Point2D point0, Point2D point1){
         this.color = color;