// @Override public synchronized void tick() { ArrayList<Element> d = new ArrayList<>(); for (Player l : jugadores) { l.tick(); } for (Player z : jugadores) { for (Element x : restriccion) { // To avoid player go outside the arena. tickUp(z, x, d); tickDown(z, x, d); tickRight(z, x, d); tickLeft(z, x, d); } } restriccion.removeAll(d); }