// Author: Joshua Ferrell
// Date: 3/25/2017

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.geometry.HPos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;

A program that caculates the return on an investment.

public class Exercise15_5 extends Application {

    // globals
    private TextField tfInvestmentAmount = new TextField();
    private TextField tfNumYears = new TextField();
    private TextField tfAnnualInterestRate = new TextField();
    private TextField tfFutureValue = new TextField();
    private Button btCalc = new Button("Calculate");

    @Override
    public void start(Stage primaryStage) {

        // Create UI
        GridPane gridPane = new GridPane();
        gridPane.setHgap(5);
        gridPane.setVgap(5);
        gridPane.add(new Label("Investment Amount:"), 0, 0);
        gridPane.add(tfInvestmentAmount, 1, 0);
        gridPane.add(new Label("Number of Years:"), 0, 1);
        gridPane.add(tfNumYears, 1, 1);
        gridPane.add(new Label("Annual Interest Rate:"), 0, 2);
        gridPane.add(tfAnnualInterestRate, 1, 2);
        gridPane.add(new Label("Future Value:"), 0, 3);
        gridPane.add(tfFutureValue, 1, 3);
        gridPane.add(btCalc, 1, 4);

        // Set Properties for UI
        gridPane.setAlignment(Pos.CENTER);
        tfInvestmentAmount.setAlignment(Pos.BOTTOM_RIGHT);
        tfNumYears.setAlignment(Pos.BOTTOM_RIGHT);
        tfAnnualInterestRate.setAlignment(Pos.BOTTOM_RIGHT);
        tfFutureValue.setAlignment(Pos.BOTTOM_RIGHT);
        tfFutureValue.setEditable(false);
        gridPane.setHalignment(btCalc, HPos.RIGHT);

        // Process event (caculate future value)
        btCalc.setOnAction(e -> calculateFutureValue());

        // Create a scene and place it in the stage
        primaryStage.setScene(new Scene(gridPane, 300, 200));
        primaryStage.setTitle("Exercise15_05"); // Set Title
        primaryStage.show(); // Display the Stage
    }

    private void calculateFutureValue() {

        // Get Values from text fields
        double amount = Double.parseDouble(tfInvestmentAmount.getText());
        double interest = Double.parseDouble(tfAnnualInterestRate.getText());
        int years = Integer.parseInt(tfNumYears.getText());

        // Get Monthly interest rate
        double monthlyInterestRate = interest / 12 / 100;

        // Get Future Value
        double futureValue = amount * Math.pow(1 + monthlyInterestRate, years * 12);

        tfFutureValue.setText(String.format("$%.2f", futureValue));
    }
}