public void saveToFile(File f) {
		try {
			ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(f));
			for (Osoba osoba : data) {
				outputStream.writeObject(osoba);
			}
			outputStream.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}