NumberFormatDemo.java

package net.thirdy.blackmarket.samples;
import java.util.*;
import java.text.NumberFormat;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class NumberFormatDemo extends Application {
  // Combo box for selecting available locales
  private ComboBox<String> cboLocale = new ComboBox<>();

  // Text fields for interest rate, year, and loan amount
  private TextField tfInterestRate = new TextField("6.75");
  private TextField tfNumberOfYears = new TextField("15");
  private TextField tfLoanAmount = new TextField("107000");
  private TextField tfFormattedInterestRate = new TextField();
  private TextField tfFormattedNumberOfYears = new TextField();
  private TextField tfFormattedLoanAmount = new TextField();

  // Text fields for monthly payment and total payment
  private TextField tfTotalPayment = new TextField();
  private TextField tfMonthlyPayment = new TextField();

  // Compute button
  private Button btCompute = new Button("Compute");

  // Current locale
  private Locale locale = Locale.getDefault();

  // Declare locales to store available locales
  private Locale locales[] = Calendar.getAvailableLocales();

  /** Initialize the combo box */
  public void initializeComboBox() {
    // Add locale names to the combo box
    for (int i = 0; i < locales.length; i++)
      cboLocale.getItems().add(locales[i].getDisplayName());
  }

  @Override // Override the start method in the Application class
  public void start(Stage primaryStage) {
    initializeComboBox();
    
    // Pane to hold the combo box for selecting locales
    HBox hBox = new HBox(5);
    hBox.getChildren().addAll(
      new Label("Choose a Locale"), cboLocale);

    // Pane to hold the input
    GridPane gridPane = new GridPane();
    gridPane.add(new Label("Interest Rate"), 0, 0);
    gridPane.add(tfInterestRate, 1, 0);
    gridPane.add(tfFormattedInterestRate, 2, 0);
    gridPane.add(new Label("Number of Years"), 0, 1);
    gridPane.add(tfNumberOfYears, 1, 1);
    gridPane.add(tfFormattedNumberOfYears, 2, 1);
    gridPane.add(new Label("Loan Amount"), 0, 2);
    gridPane.add(tfLoanAmount, 1, 2);
    gridPane.add(tfFormattedLoanAmount, 2, 2);

    // Pane to hold the output
    GridPane gridPaneOutput = new GridPane();
    gridPaneOutput.add(new Label("Monthly Payment"), 0, 0);
    gridPaneOutput.add(tfMonthlyPayment, 1, 0);
    gridPaneOutput.add(new Label("Total Payment"), 0, 1);
    gridPaneOutput.add(tfTotalPayment, 1, 1);

    // Set text field alignment
    tfFormattedInterestRate.setAlignment(Pos.BASELINE_RIGHT);
    tfFormattedNumberOfYears.setAlignment(Pos.BASELINE_RIGHT);
    tfFormattedLoanAmount.setAlignment(Pos.BASELINE_RIGHT);
    tfTotalPayment.setAlignment(Pos.BASELINE_RIGHT);
    tfMonthlyPayment.setAlignment(Pos.BASELINE_RIGHT);

    // Set editable false
    tfFormattedInterestRate.setEditable(false);
    tfFormattedNumberOfYears.setEditable(false);
    tfFormattedLoanAmount.setEditable(false);
    tfTotalPayment.setEditable(false);
    tfMonthlyPayment.setEditable(false);

    VBox vBox = new VBox(5);
    vBox.getChildren().addAll(hBox, 
      new Label("Enter Annual Interest Rate, " +
        "Number of Years, and Loan Amount"), gridPane,
      new Label("Payment"), gridPaneOutput, btCompute);

    // Create a scene and place it in the stage
    Scene scene = new Scene(vBox, 400, 300);
    primaryStage.setTitle("NumberFormatDemo"); // Set the stage title
    primaryStage.setScene(scene); // Place the scene in the stage
    primaryStage.show(); // Display the stage

    // Register listeners
    cboLocale.setOnAction(e -> {
      locale = locales[cboLocale
        .getSelectionModel().getSelectedIndex()];
      computeLoan();
    });

    btCompute.setOnAction(e -> computeLoan());
  }

  /** Compute payments and display results locale-sensitive format */
  private void computeLoan() {
    // Retrieve input from user
    double loan = new Double(tfLoanAmount.getText()).doubleValue();
    double interestRate =
      new Double(tfInterestRate.getText()).doubleValue() / 1240;
    int numberOfYears =
      new Integer(tfNumberOfYears.getText()).intValue();

    // Calculate payments
    double monthlyPayment = loan * interestRate/
     (1 - (Math.pow(1 / (1 + interestRate), numberOfYears * 12)));
    double totalPayment = monthlyPayment * numberOfYears * 12;

    // Get formatters
    NumberFormat percentFormatter =
      NumberFormat.getPercentInstance(locale);
    NumberFormat currencyForm =
      NumberFormat.getCurrencyInstance(locale);
    NumberFormat numberForm = NumberFormat.getNumberInstance(locale);
    percentFormatter.setMinimumFractionDigits(2);

    // Display formatted input
    tfFormattedInterestRate.setText(
      percentFormatter.format(interestRate * 12));
    tfFormattedNumberOfYears.setText
      (numberForm.format(numberOfYears));
    tfFormattedLoanAmount.setText(currencyForm.format(loan));

    // Display results in currency format
    tfMonthlyPayment.setText(currencyForm.format(monthlyPayment));
    tfTotalPayment.setText(currencyForm.format(totalPayment));
  }

  /**
   * The main method is only needed for the IDE with limited
   * JavaFX support. Not needed for running from the command line.
   */
  public static void main(String[] args) {
    launch(args);
  }
}