JavaFX Example - Future Value

FutureValue.java

package fvcalc;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class FutureValue extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("fv_calc.fxml"));
        primaryStage.setTitle("Future Value of Investment Calculator");
        primaryStage.setScene(new Scene(root, 400, 275));
        primaryStage.show();
    }


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

fv_calc.fxml

<?import javafx.collections.FXCollections?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import java.lang.String?>
<?import java.net.URL?>
<GridPane fx:controller="fvcalc.FVController"
          xmlns:fx="http://javafx.com/fxml" alignment="center" hgap="10" vgap="8">
    <padding><Insets top="40" right="25" bottom="10" left="35"/></padding>
    <Label text="Initial Investment:"
           GridPane.columnIndex="0" GridPane.rowIndex="0"/>
    <TextField fx:id="textInvestment"
               GridPane.columnIndex="1" GridPane.rowIndex="0"/>
    <Label text="Interest Rate:"
           GridPane.columnIndex="0" GridPane.rowIndex="1"/>
    <TextField fx:id="textRate" GridPane.columnIndex="1" GridPane.rowIndex="1"/>
    <Label text="Years:"
           GridPane.columnIndex="0" GridPane.rowIndex="2"/>
    <TextField fx:id="textYears"
               GridPane.columnIndex="1" GridPane.rowIndex="2"/>
    <Label text="Compounded:"
           GridPane.columnIndex="0" GridPane.rowIndex="3"/>
    <ComboBox fx:id="comboCompound"
              GridPane.columnIndex="1" GridPane.rowIndex="3"
              onAction="#getSelected">
        <items><FXCollections fx:factory="observableArrayList">
            <String fx:value="Yearly"/>
            <String fx:value="Biannually"/>
            <String fx:value="Quarterly"/>
            <String fx:value="Monthly"/>
            <String fx:value="Weekly"/>
            <String fx:value="Daily"/>
        </FXCollections></items>
        <value><String fx:value="Yearly"/></value>
    </ComboBox>
    <Button text="Calculate"
            GridPane.columnIndex="1" GridPane.rowIndex="4"
            onAction="#calculate"/>
    <Label fx:id="result" id="result_text" GridPane.columnIndex="0" GridPane.rowIndex="5"
           GridPane.columnSpan="3"/>
    <stylesheets>
        <URL value="@fv_style.css"/>
    </stylesheets>
</GridPane>

fv_style.css

.root {
    -fx-background-image: url("yellow_lined.png");
    -fx-background-size: stretch;
}

.label {
    -fx-font-family: "sans-serif";
    -fx-font-size: 14px;
    -fx-font-weight: bold;
    -fx-font-style: italic;
}

.text-field {
    -fx-font-family: "Verdana";
    -fx-font-size: 12px;
}

#result_text {
    -fx-font-family: "Arial Black";
    -fx-font-size: 24px;
    -fx-text-fill: red;
    -fx-effect: dropshadow( gaussian , black , 2,0.2,0,1);
}

FVController.java

package fvcalc;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import logic.FVLogic;
import logic.FVLogic.CompoundType;


public class FVController {
    @FXML private Label result;                 // these fields here
    @FXML private TextField textInvestment;     // must be declared with the
    @FXML private TextField textRate;           // @FXML annotation
    @FXML private TextField textYears;          // so they can be referenced
    @FXML private ComboBox<String> comboCompound; // from the FXML document


    private CompoundType comp = CompoundType.YEARLY;   // current type of compounding interest

    @FXML public void calculate(ActionEvent event) {
        double principal = getDouble(textInvestment.getText());
        double rate = getDouble(textRate.getText());
        double years = getDouble(textYears.getText());
        if (principal > 0 && rate > 0 && years > 0) {
            double calc = FVLogic.futureValue(principal, rate, (int) years, comp);
            result.setText("$ " + String.format("%,.2f", calc));
        }
        else {
            result.setText("Invalid Entry.");
        }
    }

    private double getDouble(String text) {
        if (text.length() > 0) {
            double d;
            try {
                d = Double.parseDouble(text);
                return d;
            }
            catch (NumberFormatException e) {
                return 0.0;
            }
        }
        return 0.0;
    }

    @FXML public void getSelected(ActionEvent e) {
        comp = FVLogic.CompoundType.valueOf(comboCompound.getSelectionModel().getSelectedItem().toUpperCase());
    }
}

FVLogic.java

package logic;

/**
 * @author /u/Philboyd_Studge on 3/27/2017.
 */
public class FVLogic {
    public enum CompoundType {
        YEARLY(1), BIANNUALLY(2), QUARTERLY(4), MONTHLY(12), WEEKLY(52), DAILY(356);
        private int compounding;
        CompoundType(int compounding) { this.compounding = compounding; }
        public int getCompounding() { return compounding; }
    }

    public static double futureValue(double investment, double rate, int periods, CompoundType cmp) {
        rate = 1 + (rate / 100) / cmp.getCompounding();
        periods *= cmp.getCompounding();

        // FV = PV * R^n
        return investment * Math.pow(rate, periods);
    }
}

How would you convert this to a Present Value calculator?