JOptionPane.showMessageDialog does not work

I try to display a message dialog approving the success or otherwise of my Java program with the database. I used different ways to see if it is successfully connected or not. and yeah it the connection is successful but I do not get a message dialog approving it. I am using Eclipse on Mac. Here is my controller Class. Please help!

package application;

import java.net.URL; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ResourceBundle; import java.util.logging.Level; import java.util.logging.Logger; import javax.swing.JOptionPane; import javafx.event.ActionEvent; import javafx.fxml.FXML; import javafx.fxml.Initializable; import javafx.scene.control.Button; import javafx.scene.control.TextField;

public class SampleController implements Initializable {

 @FXML
    private Button btnLogin;

    @FXML
    private Button btnSignUp;

    @FXML
    private TextField txtGender;

    @FXML
    private TextField txtEmail;

    @FXML
    private TextField txtFullName;

    @FXML
    private TextField txtLoginEmail;

    @FXML
    private TextField txtLoginPassword;

    @FXML
    private TextField txtPassword;

    @FXML
    private TextField txtRePassword;

    private Connection conn = null;
    PreparedStatement pst = null;
    ResultSet rs = null;
    
    @FXML
    void fcnBtnLogin(ActionEvent event) 

        conn = dbConnection.connect();
        
        String sql = "Select * from tblSignUp where EMAIL=? AND PASSWORD=?";
        
        try {
            pst =conn.prepareStatement(sql);
            pst.setString(1, txtLoginEmail.getText());
            pst.setString(2, txtLoginPassword.getText());
            
            ResultSet rs = pst.executeQuery();
            if(rs.next() == true) {
                
                JOptionPane.showMessageDialog(null, "Login Successful!");
                
            }else {
                JOptionPane.showMessageDialog(null, "Login Unuccessful! Incorrect Username or Password");
            }
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    @FXML
    void fcnBtnSignUp(ActionEvent event) {
        
        conn = dbConnection.connect();
        
        String sql = "insert into tblSignUp (FULL_NAME, GENDER, EMAIL, PASSWORD, RE_PASSWORD) values (?,?,?,?,?)";
 
        
        try {
            pst= conn.prepareStatement(sql);
            
            pst.setString(1, txtFullName.getText());
            pst.setString(2, txtGender.getText());
            pst.setString(3, txtEmail.getText());
            pst.setString(4, txtPassword.getText());
            pst.setString(5, txtRePassword.getText());
            
            pst.execute();
            
            JOptionPane.showMessageDialog(null, "!");
            
        } catch (SQLException ex) {
            Logger.getLogger(SampleController.class.getName()) . log(Level.SEVERE, null,ex);

        }
    }

public void initialize(URL url, ResourceBundle rb) {
    
}

}