The Future Value application with data validation

import java.util.*;
import java.text.*;

public class FutureValueApp
{
    public static void main(String[] args)
    {
        System.out.println(
            "Welcome to the Future Value Calculator\n");

        Scanner sc = new Scanner(System.in);
        String choice = "y";
        while (choice.equalsIgnoreCase("y"))
        {
            System.out.println("DATA ENTRY");
            double monthlyInvestment = getDoubleWithinRange(sc,
                "Enter monthly investment: ", 0, 1000);
            double interestRate = getDoubleWithinRange(sc,
                "Enter yearly interest rate: ", 0, 30);
            int years = getIntWithinRange(sc,
                "Enter number of years: ", 0, 100);
            double monthlyInterestRate = interestRate/12/100;
            int months = years * 12;
            double futureValue = calculateFutureValue(
                monthlyInvestment, monthlyInterestRate, months);

            NumberFormat currency =
                NumberFormat.getCurrencyInstance();
            NumberFormat percent =
                NumberFormat.getPercentInstance();
            percent.setMinimumFractionDigits(1);

            String results =
                  "Monthly investment:\t"
                      + currency.format(monthlyInvestment) + "\n"
                + "Yearly interest rate:\t"
                      + percent.format(interestRate/100) + "\n"
                + "Number of years:\t"
                      +  years + "\n"
                + "Future value:\t\t"
                      + currency.format(futureValue) + "\n";
            System.out.println();
            System.out.println("FORMATTED RESULTS");
            System.out.println(results);

            System.out.print("Continue? (y/n): ");
            choice = sc.next();
            sc.nextLine();
                     // discard any other data entered on the line
            System.out.println();
        }
    }

    public static double getDouble(Scanner sc, String prompt)
    {
        double d = 0.0;
        boolean isValid = false;
        while (isValid == false)
        {
            System.out.print(prompt);
            if (sc.hasNextDouble())
            {
                d = sc.nextDouble();
                isValid = true;
            }
            else
            {
                System.out.println
                    ("Error! Invalid decimal value. Try again.");
            }
            sc.nextLine();
                    // discard any other data entered on the line
        }
        return d;
    }

    public static double getDoubleWithinRange(Scanner sc,
    String prompt, double min, double max)
    {
        double d = 0.0;
        boolean isValid = false;
        while (isValid == false)
        {
            d = getDouble(sc, prompt);
            if (d <= min)
            {
                System.out.println(
                    "Error! Number must be greater than "
                    + min + ".");
            }
            else if (d >= max)
            {
                System.out.println(
                    "Error! Number must be less than " + max + ".");
            }
            else
                isValid = true;
        }
        return d;
    }

    public static int getInt(Scanner sc, String prompt)
    {
        int i = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            System.out.print(prompt);
            if (sc.hasNextInt())
            {
                i = sc.nextInt();
                isValid = true;
            }
            else
            {
                System.out.println
                    ("Error! Invalid integer value. Try again.");
            }
            sc.nextLine();
                      // discard any other data entered on the line
        }
        return i;
    }

    public static int getIntWithinRange(Scanner sc, String prompt,
    int min, int max)
    {
        int i = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            i = getInt(sc, prompt);
            if (i <= min)
                System.out.println(
                    "Error! Number must be greater than "
                    + min + ".");
            else if (i >= max)
                System.out.println(
                    "Error! Number must be less than " + max + ".");
            else
                isValid = true;
        }
        return i;
    }

    public static double calculateFutureValue(
    double monthlyInvestment, double monthlyInterestRate,
    int months)
    {
        double futureValue = 0;
        for (int i = 1; i <= months; i++)
        {
            futureValue =
                (futureValue + monthlyInvestment) *
                (1 + monthlyInterestRate);
        }
        return futureValue;
    }
}