javafx adding all subtotal of all column in tableview

Question

I have Tableview here that allows me to multiply the price and the quantity and put that into the subtotal column my question is i want to get the sum of all the subtotals for all the items in the table , thanks

private TableView<Product> table = new TableView<Product>();
private final ObservableList<Product> data =
        FXCollections.observableArrayList(
                new Product("Notebook", 10, 12),
                new Product("Eraser", 20, 12),
                new Product("Pencil", 30, 12),
                new Product("Pen", 40, 12),
                new Product("Glue", 50, 12));
final HBox hb = new HBox();

public static void main(String[] args) {
    launch(args);
}

@Override
public void start(Stage stage) {
    Scene scene = new Scene(new Group());
    stage.setTitle("Book Store Sample");
    stage.setWidth(650);
    stage.setHeight(550);

    final Label label = new Label("Book Store");
    label.setFont(new Font("Arial", 20));

    table.setEditable(true);


    TableColumn name = new TableColumn("Name");
    name.setMinWidth(100);
    name.setCellValueFactory(
            new PropertyValueFactory<Product, String>("name"));
    name.setCellFactory(TextFieldTableCell.forTableColumn());
    name.setOnEditCommit(
            new EventHandler<CellEditEvent<Product, String>>() {
                @Override
                public void handle(CellEditEvent<Product, String> t) {
                    ((Product) t.getTableView().getItems().get(
                            t.getTablePosition().getRow())
                    ).setName(t.getNewValue());
                }
            }
    );


    TableColumn priceCol = new TableColumn("Price");
    priceCol.setMinWidth(100);
    priceCol.setCellValueFactory(
            new PropertyValueFactory<Product, String>("price"));
    priceCol.setCellFactory(TextFieldTableCell.<Product, Number>forTableColumn(new NumberStringConverter()));
    priceCol.setOnEditCommit(
            new EventHandler<CellEditEvent<Product, Number>>() {
                @Override
                public void handle(CellEditEvent<Product, Number> t) {
                    ((Product) t.getTableView().getItems().get(
                            t.getTablePosition().getRow())
                    ).setPrice(t.getNewValue().intValue());
                }
            }
    );

    TableColumn quantityCol = new TableColumn("Quantity");
    quantityCol.setMinWidth(200);
    quantityCol.setCellValueFactory(
            new PropertyValueFactory<Product, Number>("quantity"));
    quantityCol.setCellFactory(TextFieldTableCell.<Product, Number>forTableColumn(new NumberStringConverter()));
    quantityCol.setOnEditCommit(
            new EventHandler<CellEditEvent<Product, Number>>() {
                @Override
                public void handle(CellEditEvent<Product, Number> t) {
                    ((Product) t.getTableView().getItems().get(
                            t.getTablePosition().getRow())
                    ).setQuantity(t.getNewValue().intValue());
                }
            }
    );

    TableColumn subTotalCol = new TableColumn("Sub Total");
    subTotalCol.setMinWidth(200);
    subTotalCol.setCellValueFactory(
            new PropertyValueFactory<Product, String>("subTotal"));


    table.setItems(data);
    table.getColumns().addAll(name, priceCol, quantityCol, subTotalCol);

    final TextField addName = new TextField();
    addName.setPromptText("Name");
    addName.setMaxWidth(name.getPrefWidth());
    final TextField addPrice = new TextField();
    addPrice.setMaxWidth(priceCol.getPrefWidth());
    addPrice.setPromptText("Price");
    final TextField addQuantity = new TextField();
    addQuantity.setMaxWidth(quantityCol.getPrefWidth());
    addQuantity.setPromptText("Quantity");

    final Button addButton = new Button("Add");
    addButton.setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent e) {
            data.add(new Product(
                    name.getText(),
                    Integer.parseInt(addPrice.getText()),
                    Integer.parseInt(addQuantity.getText())));
            addName.clear();
            addPrice.clear();
            addQuantity.clear();
        }
    });

    hb.getChildren().addAll(addName, addPrice, addQuantity, addButton);
    hb.setSpacing(3);

    final VBox vbox = new VBox();
    vbox.setSpacing(5);
    vbox.setPadding(new Insets(10, 0, 0, 10));
    vbox.getChildren().addAll(label, table, hb);

    ((Group) scene.getRoot()).getChildren().addAll(vbox);

    stage.setScene(scene);
    stage.show();
}

public static class Product {

    private final SimpleStringProperty name;
    private final SimpleIntegerProperty price;
    private final SimpleIntegerProperty quantity;
    private final SimpleIntegerProperty subTotal;

    private Product(String name, int price, int quantity) {
        this.name = new SimpleStringProperty(name);
        this.price = new SimpleIntegerProperty(price);
        this.quantity = new SimpleIntegerProperty(quantity);
        this.subTotal = new SimpleIntegerProperty();
        NumberBinding multiplication = Bindings.multiply(this.priceProperty(), this.quantityProperty());
        this.subTotalProperty().bind(multiplication);
    }

    public String getName() {
        return name.get();
    }

    public SimpleStringProperty nameProperty() {
        return name;
    }

    public void setName(String name) {
        this.name.set(name);
    }

    public int getPrice() {
        return price.get();
    }

    public SimpleIntegerProperty priceProperty() {
        return price;
    }

    public void setPrice(int price) {
        this.price.set(price);
    }

    public int getQuantity() {
        return quantity.get();
    }

    public SimpleIntegerProperty quantityProperty() {
        return quantity;
    }

    public void setQuantity(int quantity) {
        this.quantity.set(quantity);
    }

    public int getSubTotal() {
        return subTotal.get();
    }

    public SimpleIntegerProperty subTotalProperty() {
        return subTotal;
    }

    public void setSubTotal(int subTotal) {
        this.subTotal.set(subTotal);
    }
}

}

Answer 1

You can create a binding that tracks the total of all the subtotal values:

IntegerBinding total = Bindings.createIntegerBinding(() -> 
    table.getItems().stream().collect(Collectors.summingInt(Product::getSubTotal)),
    table.getItems());

The first parameter to this is a function that computes the total of the results of calling product.getSubTotal() on each element in table.getItems(). The second argument ensures that this binding is marked as invalid (so can be recomputed) any time table.getItems() is invalidated.

Using the default mechanism of constructing a list, as you do with ObservableList<Product> data = FXCollections.observableArrayList(...), the list will only be invalidated when items are added, removed, or replaced, but not if the subTotal of an existing item changes. To make this happen, you need to modify that line to use a extractor:

private final ObservableList<Product> data = FXCollections.observableList(Arrays.asList(
    new Product("Notebook", 10, 12),
    new Product("Eraser", 20, 12),
    new Product("Pencil", 30, 12),
    new Product("Pen", 40, 12),
    new Product("Glue", 50, 12)),
    product -> new Observable[] {product.subTotalProperty()});

Now you can do something like

Label totalLabel = new Label();
totalLabel.textProperty().bind(Bindings.format("Total: %d", total));

Update

Here is what the IntegerBinding code looks like without a lambda expression, though it is far less clear and I don't recommend doing this:

IntegerBinding total = Bindings.createIntegerBinding(new Callable<Integer>() {
    @Override
    public Integer call() {
        return table.getItems().stream().collect(Collectors.summingInt(
            new ToIntFunction<Product>() {
                @Override
                public int applyAsInt(Product product) {
                    return product.getSubTotal();
                }
            }));
    }
}, table.getItems());