public void chackData(){
        try {

    Class.forName("com.mysql.jdbc.Driver").newInstance();
    con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mylibrary_db","root", "");
    String sql = "SELECT * FROM db ;";
            pst = con.prepareStatement(sql);
            rs = pst.executeQuery();
            String s ="";
            while(rs.next()){
                 s = rs.getString("Db");
            System.out.println(s);
            }
    con.close();