使用tableview的贷款计算器在JavaFX

Question

我正在尝试制作一个贷款计算器，在JavaFX中显示tableview中的付款编号，利息，本金和余额。现在只填充主要和余额列。我是JavaFX的新手，所以我不确定我是否在FX或我的公式中犯了错误。这是我的代码：

public class LoanTable extends Application {
Integer payment;
Double interest;
Double principal;
Double balance;
@Override 
public void start(Stage primaryStage) {
    BorderPane border = new BorderPane();
    GridPane grid = new GridPane();
    ScrollPane scroll = new ScrollPane();
    Label labelTitle = new Label("Enter Loan Amount, Number of Years, and     Annual Interest Rate");
    labelTitle.getStyleClass().add("labelTitle");
    Label loan = new Label("Loan Amount");
    TextField loanAmount = new TextField();
    Label years = new Label("Number of Years");
    TextField numYears = new TextField();
    Label interestRate = new Label("Annual Interest Rate");
    TextField rate = new TextField();
    Button compute = new Button("Display Loan Schedule");

    TableView<Finance> table = new TableView<>();

    TableColumn paymentColumn = new TableColumn("Payment#");
    paymentColumn.setMinWidth(200);
    paymentColumn.setCellValueFactory(new PropertyValueFactory<Finance, Integer>("payment"));

    TableColumn interestColumn = new TableColumn("Interest");
    interestColumn.setMinWidth(200);
    interestColumn.setCellValueFactory(new PropertyValueFactory<Finance, Double>("interest"));

    TableColumn prinColumn = new TableColumn("Principal");
    prinColumn.setMinWidth(200);
    prinColumn.setCellValueFactory(new PropertyValueFactory<Finance, Double>("principal"));

    TableColumn balColumn = new TableColumn("Balance");
    balColumn.setMinWidth(200);
    balColumn.setCellValueFactory(new PropertyValueFactory<Finance, Double>("balance"));

    table.getColumns().addAll(paymentColumn, interestColumn, prinColumn, balColumn);

    grid.add(labelTitle, 0, 0);
    grid.add(new Label(), 0, 1);
    grid.add(loan, 0, 2);
    grid.add(loanAmount, 1, 2);
    grid.add(years, 0, 3);
    grid.add(numYears, 1, 3);
    grid.add(interestRate, 0, 4);
    grid.add(rate, 1, 4);
    grid.add(compute, 4, 0);

    scroll.setContent(table);

    border.setTop(grid);
    border.setBottom(scroll);

    Scene scene = new Scene(border, 800, 800);
    scene.getStylesheets().add("loan_table.css");

    primaryStage.setScene(scene);
    primaryStage.show();

    compute.setOnAction((e) -> {
        Double loanTotal = Double.parseDouble(loanAmount.getText());
        Integer year = Integer.parseInt(numYears.getText());
        Double rateInterest = Double.parseDouble(rate.getText());
        double monthlyInterest = rateInterest / 1200;
        double monthlyPayment = loanTotal * monthlyInterest / (1 - 1 / Math.pow(1 + monthlyInterest, year * 12));
        balance = loanTotal;

        for(int i = 1; i < year * 12; i++) {
             interest = monthlyInterest * balance;
             principal = monthlyPayment - interest;
             balance = balance - principal;
             payment = i + 1;
        }

        ObservableList<Finance> data = FXCollections.observableArrayList(new Finance(payment, interest, principal, balance));
        table.setItems(data);

    });

}

public static class Finance {
    private final SimpleIntegerProperty payment;
    private final SimpleDoubleProperty interest;
    private final SimpleDoubleProperty principal;
    private final SimpleDoubleProperty balance;

    private Finance(int payment, double interest, double principal, double balance) {
        this.payment = new SimpleIntegerProperty(payment);
        this.interest = new SimpleDoubleProperty(interest);
        this.principal = new SimpleDoubleProperty(principal);
        this.balance = new SimpleDoubleProperty(balance);
    }

    public Integer getPayment(int numYears) {
        return payment.get();
    }

    public Double getInterest(double rate) {

        return interest.get();
    }

    public Double getPrincipal() {
        return principal.get();
    }

    public Double getBalance() {
        return balance.get();
    }
}

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

}