The Decorator class adds functionality to the shapes. It also implements Shape...

The Decorator class adds functionality to the shapes. It also implements Shape and delegates method calls to the decorated shape.

src/main/java/shape/Decorator.java

+package shape;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.geometry.Point2D;
+
+public abstract class Decorator implements Shape {
+    protected Shape decoratedShape;
+
+    public Decorator(Shape decoratedShape) {
+        this.decoratedShape = decoratedShape;
+    }
+
+    @Override
+    public int pointsCount() {
+        return decoratedShape.pointsCount();
+    }
+
+    @Override
+    public Point2D point(int index) {
+        return decoratedShape.point(index);
+    }
+
+    @Override
+    public void draw(GraphicsContext graphicsContext) {
+        decoratedShape.draw(graphicsContext);
+        drawDecoration(graphicsContext);
+    }
+
+    protected abstract void drawDecoration(GraphicsContext graphicsContext);
+}