UPDATE multiple records in mysql from javafx after checkout in cart

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Java

MySQL

database

JavaFX

I am having a cart page where users can checkout after purchasing the products/medicines. I am having a button named checkout on that page. After clicking that button "CheckOut" I want to update multiple records in MySQL from JavaFX after clicking that button. I want the quantity of each item/medicine in the tableView to decreased according to the quantity purchased. I have tried putting the query in for loop I tried to selectAll from the table view. I will provide the code I wrote and a screenshot from the JavaFX tableView with the buttons. Any help is appreciated. Thanks for your time and cooperation from now.

package Patient;

import Admin.Doctor.AddDoctor;
import com.jfoenix.controls.JFXButton;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.control.SelectionMode;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.StackPane;


import java.sql.PreparedStatement;

import static Admin.AdminLogin.rightDown;
import static Connection.DBConnection.*;
import static sample.ChoicePage.scene;

public class CompletePurchase
{
    private StackPane tablePane;
    private TableView<Cart> cartTableView;

    private JFXButton remove;
    private JFXButton complete;

    public void complete()
    {
        rightDown.getChildren().clear();

        new AddDoctor().back();

        tablePane = new StackPane();
        tablePane.setMinWidth(700);
        tablePane.setMinHeight(500);
        tablePane.setLayoutY(90);
        tablePane.setLayoutX(150);

        tablePane.getChildren().clear();

        remove = new JFXButton("REMOVE");
        remove.setPrefWidth(200);
        remove.setPrefHeight(35);
        remove.setLayoutX(300);
        remove.setLayoutY(600);
        remove.getStyleClass().add("loginButton");
        remove.setOnAction((e)->{
            try
            {
                Cart cart = cartTableView.getSelectionModel().getSelectedItem();

                String removeQuery = "DELETE FROM Cart WHERE MedicineID = ?";
                preparedStatement = connection.prepareStatement(removeQuery);
                preparedStatement.setString(1,cart.getMedicineID());
                preparedStatement.executeUpdate();
                preparedStatement.close();

                cartTableView.getItems().removeAll(cartTableView.getSelectionModel().getSelectedItem());
            }
            catch(Exception e1)
            {
                e1.printStackTrace();
            }
        });
        rightDown.getChildren().add(remove);

        complete = new JFXButton("CHECKOUT");
        complete.setPrefWidth(200);
        complete.setPrefHeight(35);
        complete.setLayoutX(600);
        complete.setLayoutY(600);
        complete.getStyleClass().add("loginButton");
        complete.setOnAction((e)->{
            try
            {
                cartTableView.getSelectionModel().selectAll();
                int num = cartTableView.getItems().size();
                Cart cart = cartTableView.getSelectionModel().getSelectedItem();

                String updateQuery = "UPDATE Medicine SET Quantity = Quantity - ? WHERE MedicineID = ?";
                preparedStatement = connection.prepareStatement(updateQuery);
                preparedStatement.setString(1,cart.getQuantity());
                preparedStatement.setString(2,cart.getMedicineID());

                preparedStatement.executeUpdate();
                preparedStatement.close();
            }

            catch(Exception e1)
            {
                e1.printStackTrace();
            }
        });
        rightDown.getChildren().add(complete);

        ObservableList<Cart> cartObservableList = FXCollections.observableArrayList();

        TableColumn<Cart,String> PatientID = new TableColumn<>("PATIENT ID");
        PatientID.setCellValueFactory(new PropertyValueFactory<>("PatientID"));
        PatientID.setPrefWidth(116);

        TableColumn<Cart,String> MedicineID = new TableColumn<>("MEDICINE ID");
        MedicineID.setCellValueFactory(new PropertyValueFactory<>("MedicineID"));
        MedicineID.setPrefWidth(116);

        TableColumn<Cart,String> MedicineName = new TableColumn<>("MEDICINE NAME");
        MedicineName.setCellValueFactory(new PropertyValueFactory<>("MedicineName"));
        MedicineName.setPrefWidth(116);

        TableColumn<Cart,String> Price = new TableColumn<>("PRICE");
        Price.setCellValueFactory(new PropertyValueFactory<>("Price"));
        Price.setPrefWidth(116);

        TableColumn<Cart,String> Quantity = new TableColumn<>("QUANTITY");
        Quantity.setCellValueFactory(new PropertyValueFactory<>("Quantity"));
        Quantity.setPrefWidth(116);

        TableColumn<Cart,String> TotalPrice = new TableColumn<>("TOTAL PRICE");
        TotalPrice.setCellValueFactory(new PropertyValueFactory<>("TotalPrice"));
        TotalPrice.setPrefWidth(116);

        try
        {
            resultSet = connection.createStatement().executeQuery("SELECT * FROM Cart");

            while (resultSet.next())
            {
                cartObservableList.add(new Cart(
                        resultSet.getString("PatientID"),
                        resultSet.getString("MedicineID"),
                        resultSet.getString("MedicineName"),
                        resultSet.getString("Price"),
                        resultSet.getString("Quantity"),
                        resultSet.getString("TotalPrice")
                ));
            }
        }

        catch(Exception e1)
        {
            e1.printStackTrace();
        }

        cartTableView = new TableView<>();
        cartTableView.getColumns().addAll(PatientID,MedicineID,MedicineName,Price,Quantity,TotalPrice);
        cartTableView.setItems(cartObservableList);
        cartTableView.getSelectionModel().setSelectionMode(
                SelectionMode.MULTIPLE
        );

        cartTableView.setMinWidth(700);
        cartTableView.setMinHeight(500);
        cartTableView.setLayoutY(0);
        cartTableView.setLayoutX(0);

        tablePane.getChildren().add(cartTableView);
        rightDown.getChildren().addAll(tablePane);

        scene.getStylesheets().add("Admin/Doctor/AddDoctor.css");
    }
}

What I have tried:

I have tried using for loop.
I have tried using selectALL in TableView.
But no one did work