public void save() throws IOException {
        try {
            this.mutex.acquire();

            // On enregistre le fichier
            FileWriter fw = new FileWriter(XML_PATH, false);
            BufferedWriter bw = new BufferedWriter(fw);

            bw.write("<?xml version=\"1.0\"?>");
            bw.newLine();
            bw.append("<users>");


            for (int i = 0; i < this.users.size(); i++) {
                writeUser(bw, this.users.get(i));
            }


            bw.newLine();
            bw.append("</users>");

            bw.flush();
            bw.close();

            this.mutex.release();
        } catch (InterruptedException ex) {
            Logger.getLogger(DataBase.class.getName()).log(Level.SEVERE, null, ex);
        }
    }