// registers new user and returns his instance
    public void registerUser(String login, String password, String mail, String name)
    {
        try
        {
            Statement stmt;
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/mysql";
            Connection con = DriverManager.getConnection(url,"root", "");

            System.out.println("URL: " + url); // debug
            System.out.println("Connection: " + con);

            stmt = con.createStatement();

            stmt.executeUpdate("INSERT INTO user(login, pass, mail, name) VALUES('"+login+"', '"+password+"', '"+mail+"', '"+name+"')");

            // gets last insertionid
            ResultSet rs = stmt.getGeneratedKeys();
            int lastInsertedId = rs.getInt(1);

            this.id = lastInsertedId;
            this.login = login;
            this.name = name;
            this.mail = mail;
            this.name = name;

            con.close();
         }
         catch( Exception e )
         {
             System.out.println(e.getStackTrace()); // chyba
         }
    }