JavaFX GridPane create a loan calculator

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
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.scene.layout.HBox;
import javafx.stage.Stage;

public class Main extends Application {
   @Override//  ww w  .  ja  v  a 2 s.com
   public void start(Stage primaryStage) throws Exception {

      LoanInvestCalcPane calcPane = new LoanInvestCalcPane();

      primaryStage.setScene(new Scene(calcPane, calcPane.getPrefWidth(), calcPane.getPrefHeight()));
      primaryStage.setTitle("Simple calculator");
      primaryStage.show();
   }

   public static void main(String[] args) {

      Application.launch(args);
   }

}

class LoanInvestCalcPane extends GridPane {

   Label lbInvestAmount = new Label("Invest Amount:");
   TextField tfInvestAmount = new TextField();

   Label lbNumberOfYears = new Label("Number Of Years:");
   TextField tfNumberOfYears = new TextField();

   Label lbAnnualInterestRate = new Label("Annual Interest Rate:");
   TextField tfAnnualInterestRate = new TextField();

   Label lbFutureValue = new Label("Future Value:");
   TextField tfFutureValue = new TextField();

   Button btCalc = new Button("Calculate");

   public LoanInvestCalcPane() {

      // Create layout
      setPadding(new Insets(10, 10, 10, 10));
      setAlignment(Pos.CENTER);
      setHgap(10);
      setVgap(10);

      add(lbInvestAmount, 0, 0);
      add(tfInvestAmount, 1, 0);

      add(lbNumberOfYears, 0, 1);
      add(tfNumberOfYears, 1, 1);

      add(lbAnnualInterestRate, 0, 2);
      add(tfAnnualInterestRate, 1, 2);

      add(lbFutureValue, 0, 3);
      add(tfFutureValue, 1, 3);

      HBox buttons = new HBox();
      buttons.getChildren().add(btCalc);
      buttons.setAlignment(Pos.BOTTOM_RIGHT);
      add(buttons, 1, 4);
      btCalc.setOnAction(e -> calcFutureValue());

      // Editing TextField settings
      TextField[] textFields = (TextField[]) getArray(tfInvestAmount, tfNumberOfYears, tfAnnualInterestRate,
            tfFutureValue);

      for (TextField tf : textFields) {
         tf.setAlignment(Pos.BASELINE_RIGHT);
      }
      tfFutureValue.setDisable(true);

   }

   private Object[] getArray(Object... objects) {
      Object[] temp = new TextField[objects.length];
      for (int i = 0; i < objects.length; i++) {
         temp[i] = objects[i];
      }
      return temp;
   }

   public void calcFutureValue() {
      double investmentAmount = Double.parseDouble(tfInvestAmount.getText());
      double years = Double.parseDouble(tfNumberOfYears.getText());
      double monthInterestRate = Double.parseDouble(tfAnnualInterestRate.getText()) / 12 / 100;

      double futureValue = investmentAmount * Math.pow(1 + monthInterestRate, years * 12);
      tfFutureValue.setText(String.format("$%.2f", futureValue));
   }
}