Question

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")) {
            // get the input from the user
            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);
            System.out.println();

            // calculate the future value
            double monthlyInterestRate = interestRate / 12 / 100;
            int months = years * 12;
            double futureValue = calculateFutureValue(
                    monthlyInvestment, monthlyInterestRate, months);

            // get the currency and percent formatters
            NumberFormat c = NumberFormat.getCurrencyInstance();
            NumberFormat p = NumberFormat.getPercentInstance();
            p.setMinimumFractionDigits(1);

            // format the result as a single string
            String results
              = "Monthly investment:   " + c.format(monthlyInvestment) + "\n"
              + "Yearly interest rate: " + p.format(interestRate / 100) + "\n"
              + "Number of years:      " + years + "\n"
              + "Future value:         " + c.format(futureValue) + "\n";

            // print the results
            System.out.println("FORMATTED RESULTS");
            System.out.println(results);

            // see if the user wants to continue
            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 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 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 number. Try again.");
            }
            sc.nextLine(); // discard any other data entered on the line
        }
        return d;
    }

    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 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. Try again.");
            }
            sc.nextLine(); // discard any other data entered on the line
        }
        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);
             //System.out.println("month " + i + " futureValue: " + futureValue);
        }
        return futureValue;
    }
}

In Java I am trying to test and debug this The get Double method contains syntax errors

use netbeans to find and fix them.

Then go to the calculateFutureValue method and add a println statement within the loop that prints the value of of the month and the future value each time the loop is exucuted

the Comment out the println so it no longer prints to the output window

then fix the logic error

Answer 1

import java.text.NumberFormat;
import java.util.Scanner;

public class DebugProgram {

    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")) {
            // get the input from the user
            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);
            System.out.println();

            // calculate the future value
            double monthlyInterestRate = interestRate / 12 / 100;
            int months = years * 12;
            double futureValue = calculateFutureValue(monthlyInvestment, monthlyInterestRate, months);

            // get the currency and percent formatters
            NumberFormat c = NumberFormat.getCurrencyInstance();
            NumberFormat p = NumberFormat.getPercentInstance();
            p.setMinimumFractionDigits(1);

            // format the result as a single string
            String results
                    = "Monthly investment:   " + c.format(monthlyInvestment) + "\n"
                    + "Yearly interest rate: " + p.format(interestRate / 100) + "\n"
                    + "Number of years:      " + years + "\n"
                    + "Future value:         " + c.format(futureValue) + "\n";

            // print the results
            System.out.println("FORMATTED RESULTS");
            System.out.println(results);

            // see if the user wants to continue
            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 getDoubleWithinRange(Scanner sc, String prompt,
                                              double min, double max) {
        double d = 0.0;
        boolean isValid = false;
        while (!isValid) {
            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 double getDouble(Scanner sc, String prompt) {
        double d = 0.0;
        boolean isValid = false;
        while (!isValid) {
            System.out.print(prompt);
            if (sc.hasNextDouble()) {
                d = sc.nextDouble();
                isValid = true;
            } else {
                System.out.println("Error! Invalid number. Try again.");
            }
            sc.nextLine();  // discard any other data entered on the line
        }
        return d;
    }

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

Welcome to the Future Value Calculator DATA ENTRY Enter monthly investment: Enter yearly interest rate: Enter number of years: month 1 futureValue: 505.0 month 2 futureValue: 1015.05 month 3 futureValue: 1530.2005 month 4 futureValue: 2050.502505 month 5 futureValue: 2576.00753005 month 6 futureValue: 3106.7676053504997 month 7 futureValue: 3642.835281404005 month 8 futureValue: 4184.263634218045 month 9 futureValue: 4731.106270560225 month 10 futureValue: 5283.417333265827 month 11 futureValue: 5841.251506598485 month 12 futureValue: 6404.66402166447 FORMATTED RESULTS Monthly investment: $500.00 Yearly interest rate: 12.0% Number of years: Future value: $6,404.66 Continue? (y/n): Process finished with exit code 0