Update alchemist-swingui/src/main/java/it/unibo/alchemist/boundary/swingui/monitor/impl/Generic2DDisplay.java

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: DanySK

alchemist-swingui/src/main/java/it/unibo/alchemist/boundary/swingui/monitor/impl/Generic2DDisplay.java

@@ -389,9 +389,10 @@ private void drawObstacles(final Graphics2D g) {
         /*
          * This currently draws all obstacles, even when they are fully outside the viewport.
          */
-        obstacles.parallelStream()
+        final List<Shape> obstacleShapes = obstacles.parallelStream()
             .map(this::convertObstacle)
-            .forEachOrdered(g::fill);
+            .collect(Collectors.toList());
+        obstacleShapes.forEach(g::fill);
     }
 
     private void drawLinks(final Graphics2D g, final Map<Node<T>, Point> onView) {