Nullpointerexception when generating graph

Question

I’m creating a graph that pulls data from the database, but at the time of generating the graph gives the following error:

Exception in thread "AWT-Eventqueue-0" java.lang.Nullpointerexception

The first line you accuse in error is within the method createDataset (is the first line inside the "of". That is the method:

private XYDataset createDataset(){
    XYSeries series = new XYSeries("Teste");
    conex.conectar();

    try{
    do{
        double rcv = conex.rs.getDouble("rcv_arena_verde"); 
        double rth = conex.rs.getDouble("rth_arena_verde"); 
    series.add(rcv, rth);

    } while (conex.rs.next());
    }catch (SQLException ex){ 
        JOptionPane.showMessageDialog(null, "Erro ao preencher grafico \n " +ex.getMessage());
    }

    XYSeriesCollection dataset = new XYSeriesCollection();
    dataset.addSeries(series); 
    return dataset;
} 

The methods/parameters of connection with the bank are correct, after all I use them in other classes in the same project and I have no problems. Am I using/calling them incorrectly? I have tried several things and the error persists.

EDIT

Other parts of the class for a better understanding of it:

public class GraficosArenaProceso extends javax.swing.JFrame {

ConexaoBanco conex = new ConexaoBanco();

ModeloBeansPruebasArenaEnVerde mod = new ModeloBeansPruebasArenaEnVerde();
DaoPruebasArenaEnVerde control = new DaoPruebasArenaEnVerde();


 public GraficosArenaProceso() {
    initComponents();
    initUI();
}

   private void initUI(){
    XYDataset dataset = createDataset();
    JFreeChart chart = createChart(dataset);

    ChartPanel chartPanel = new ChartPanel(chart);

    // [...] Aspectos visuais do gráfico           

}

Main method:

    public static void main(String args[]) {

    SwingUtilities.invokeLater(() -> {
        GraficosArenaProceso graficoProceso = new GraficosArenaProceso();
        graficoProceso.setVisible(true);
    } );

Answer 1

As placed by @Fábio conex.rs is null. See the method that initializes the object rs. In the same private Xydataset createDataset() class, see if at any time the conex.rs is actually initialized.

For clearer verification, compare with other methods from the beginning to the connecter call.rs.getDouble("rcv_arena_green");

If you want more help, please share the whole class.