SystemImpl(SectorImpl sector, System system) { this.sector = sector; this.system = system; for (Object planetOrStar : system.getPlanetOrStar()) { if (planetOrStar instanceof Planet) { planetOrStars.add(new PlanetImpl(this, (Planet) planetOrStar)); } else if (planetOrStar instanceof Star) { planetOrStars.add(new StarImpl(this, (Star) planetOrStar)); } } }