private boolean releaseItem(ParkingPlace place) {
		LOCK.lock();
		try {
			int index = PLACES.indexOf(place);
			if (index == -1) {
				return false;
			}
			if (PLACES.get(index).isUsed()) {
				place.togleUsed();
				return true;
			}
		} finally {
			LOCK.unlock();
		}
		return false;
	}