public LinkedHashMap<Integer, Compra> leerComprasXStream(String rutaFichero) {
        XStream xstream = new XStream();
        rutaFichero = rutaFichero + ".xml";
        LinkedHashMap<Integer, Compra> compras = new LinkedHashMap<>();
        try {
            compras = (LinkedHashMap<Integer, Compra>) xstream.fromXML(new FileInputStream(rutaFichero));
        } catch (FileNotFoundException ex) {
            //Logger.getLogger(FicherosDatos.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println("Error en leerComprasXStream");
        }
        return compras;
    }