add of BorderDecorator class , it adds a border (a circle) around each point of the shape.

src/main/java/shape/BorderDecorator.java

+package shape;
+import javafx.scene.canvas.GraphicsContext;
+import javafx.geometry.Point2D;
+import javafx.scene.paint.Color;
+
+public class BorderDecorator extends Decorator {
+    private double radius;
+
+    public BorderDecorator(Shape decoratedShape, double radius) {
+        super(decoratedShape);
+        this.radius = radius;
+    }
+
+    @Override
+    protected void drawDecoration(GraphicsContext graphicsContext) {
+        graphicsContext.setStroke(Color.BLACK);
+        for (int i = 0; i < decoratedShape.pointsCount(); i++) {
+            Point2D point = decoratedShape.point(i);
+            graphicsContext.strokeOval(point.getX() - radius, point.getY() - radius, radius * 2, radius * 2);
+        }
+    }
+}
+