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, 10000);
             double interestRate = getDoubleWithinRange(sc, "Enter yearly interest rate: ", 0, 30);
             int years = getInWithinRange(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();  
        }     
    }

// the code for the Future Value application with data validation
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 enter 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 lesser than " + max + ".");
              }
              else
                  isValid = true;
       } 
       return d;

}
//*****************************************************
// The code for the Future Value application with data validation

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 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 lesser 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;
    }

}