Create serializable file once in java

My problem is that I want to create a System-type object only the first time I start the program, the next time I want to read the saved System file.

 public static void main(String[] args) {

        Sistema sistema;
        try {
            sistema = new Sistema();

            FileOutputStream file = new FileOutputStream("archivo_sistema.txt");
            BufferedOutputStream bf = new BufferedOutputStream(file);
            ObjectOutputStream obj = new ObjectOutputStream(bf);

            obj.writeObject(sistema);
            obj.flush();
            obj.close();

            FileInputStream recuperar_file = new FileInputStream("archivo_sistema.txt");
            BufferedInputStream bi = new BufferedInputStream(recuperar_file);
            ObjectInputStream obs = new ObjectInputStream(bi);

            sistema = (Sistema)(obs.readObject());

        } catch (ClassNotFoundException | IOException e) {
            e.printStackTrace();
        }
        JFrameMenu vMenu = new JFrameMenu(sistema);

        vMenu.setVisible(true);

    }
}