Question

Your task is to create a Java application that converts a specified amount of one currency into another currency for a user. The application must meet the following requirements:

1. Upon execution, the application shall display a brief welcome message announcing that the user is running the currency converter application.
   
2. The application shall allow a user to convert amounts between any two of the following currencies: United States Dollars (USD), British Pounds (GBP), Swiss Francs (CHF), and Indian Rupees (INR).
   
3. The application shall prompt the user for the following input: the currency she wishes to convert from (“source currency”); the amount of currency to be converted (“requested amount”) as either a decimal or a whole number (e.g., 21.45, 1.748484, or 34); and the currency she wishes to convert to (“result currency”).
   
4. The application shall limit the amount of the currency to be converted to no more than 1,000,000 (one million) units of that currency; if the user attempts to enter an amount larger than this number, the application should return a message stating that the user has exceeded the maximum amount, and prompt the user to enter another amount.
   
5. The application shall handle incorrect user input (e.g., if the user inputs a character or string for the “requested amount” value) and prompt the user for correct input.
   
6. The application shall prevent the user from attempting to convert to a “result currency” that is the same as the “source currency” (e.g., the user should be prevented from converting United States Dollars to United States Dollars).
   
7. The application shall output the following information: the amount of the “result currency” that is equivalent to the “requested amount” in the “source currency”; this amount shall be returned as a decimal figure rounded to two decimal places (e.g., 67.49).
   
8. The application shall allow the user to exit the program at any time by accepting input of an exit character (for example “Q” for quit) to terminate the program.
   
9. After the user has successfully converted a currency, the application shall prompt the user to either perform another conversion or terminate the program.
   
10. Upon program termination, the application shall display an exit message to the user.

Program Data

Your program should use the following data for currency conversions.

	USD	GBP	CHF	INR
USD	1.000000	1.29498	1.09820	0.0136097
GBP	0.772268	1.000000	0.848271	0.0105101
CHF	0.910585	1.17887	1.000000	0.0123905
INR	73.4772	95.1467	80.7070	1.000000

Here is some sample data you can use to verify your calculations:

20.00 USD = 15.45 GBP

20.00 USD = 18.21 CHF

20.00 USD = 1469.54 INR

20.00 CHF = 21.96 USD

20.00 CHF = 16.97 GBP

20.00 CHF = 1614.14 INR

50.00 INR = 0.68 USD

50.00 INR = 0.53 GBP

50.00 INR = 0.62 CHF


Please note that currency rates fluctuate continuously in the real world. The table outlined above sets baseline rates that I will be using to verify your calculations. If you use online currency converters to verify your results, they may be using real-time data that will result in calculations that are different from those made using the conversion rate table above.

You may store this data in any fashion you like for this assignment. I would recommend using arrays (single-dimensional or multi-dimensional) for this purpose.

Answer 1

// CurrencyConverter.java

import java.util.InputMismatchException;
import java.util.Scanner;

public class CurrencyConverter {

   public static void main(String[] args) {

       // array to store the valid currencies
       String valid_currency[] = {"USD", "GBP", "CHF", "INR"};
      
       // array to store the conversion charts, source currency - rows, destination currency - columns
       double conversion_chart[][] = { {1.00,    0.772268 , 0.910585 , 73.4772},
                                       {1.29498, 1.00, 1.17887, 95.1467},
                                       {1.09820, 0.848271, 1,00, 80.7070},
                                       { 0.0136097, 0.0105101, 0.0123905, 1.00}};
      
       int src_index = -1, dst_index = -1;
      
       String src_currency, dst_currency, choice;
       double amount_to_convert, converted_amount;
       Scanner scan = new Scanner(System.in);
      
       // loop that continues until the user exits
       do
       {
           // input the source currency
           System.out.print("Enter the source currency(USD/GBP/CHF/INR): ");
           src_currency =scan.nextLine();
           // validate source currency and re-prompt until valid
           while(!src_currency.equalsIgnoreCase("usd") && !src_currency.equalsIgnoreCase("gbp") && !src_currency.equalsIgnoreCase("chf") && !src_currency.equalsIgnoreCase("inr"))
           {
               System.out.print("Valid currency are: USD, GBP, CHF and INR. Re-enter source currency: ");
               src_currency =scan.nextLine();
           }
          
           // input conversion amount
           System.out.print("Enter the amount to convert: ");
           // validate conversion amount and re-prompt until valid
           while(true) {
               try
               {
                   amount_to_convert = scan.nextDouble();
                   if(amount_to_convert > 1000000)
                   {
                       System.out.print("Cannot convert currency more than 1,000,000 (one million) units. Re-enter: ");
                   }else
                       break;
               }catch(InputMismatchException e)
               {
                   System.out.print("Invalid input for amount to convert. Re-enter: ");
                   scan.nextLine();
               }
           }
          
           scan.nextLine(); // ignore \n left by nextDouble
          
           // input destination currency
           System.out.print("Enter the destination currency(USD/GBP/CHF/INR): ");
           dst_currency =scan.nextLine();
           // validate destination currency and re-prompt until valid
           while(!dst_currency.equalsIgnoreCase("usd") && !dst_currency.equalsIgnoreCase("gbp") && !dst_currency.equalsIgnoreCase("chf")
                   && !dst_currency.equalsIgnoreCase("inr") || ((dst_currency.equalsIgnoreCase(src_currency))))
           {
               if(dst_currency.equalsIgnoreCase(src_currency))
                   System.out.print("Source and destination currency cannot be same. Re-enter: ");
               else
                   System.out.print("Valid currency are: USD, GBP, CHF and INR. Re-enter source currency: ");
               dst_currency =scan.nextLine();
           }
          
           // loop to get the index of source currency and destination currency in the array
           for(int i=0;i<valid_currency.length;i++)
           {
               if(valid_currency[i].equalsIgnoreCase(src_currency))
                   src_index = i;
               else if(valid_currency[i].equalsIgnoreCase(dst_currency))
                   dst_index = i;
           }
          
           // display the result of conversion
           System.out.printf("\nThe amount of the %s that is equivalent to %.2f in the %s: %.2f\n",src_currency, amount_to_convert
                       , dst_currency, (amount_to_convert*conversion_chart[src_index][dst_index]));
          
           // input the choice,if the user wants to perform another conversion or exit
           System.out.print("Perform another converion(C) or Terminate the program(Q)? ");
           choice = scan.nextLine();
           // validate choice and re-prompt if invalid
           while(!choice.equalsIgnoreCase("C") && !choice.equalsIgnoreCase("Q"))
           {
               System.out.print("Invalid input. Valid inputs are C or Q. Re-enter: ");
               choice = scan.nextLine();
           }
          
       }while(choice.equalsIgnoreCase("C"));
     
   }

}

// end of CurrencyConverter.java

Output: