Decimal Value error

Question

I'm writing a program that grabs 2 inputs from the user: 1) the price of an item 2) the amount payed. It will then return the difference of the two (change due) and it will then compute how many bills and coins would be given back. I'm having trouble when finding the decimal (coin values accurately):

int one, five, ten, twenty,qs, ds, ns, ps, rem ;
    double price, pay,change;
    String user;
    Scanner input = new Scanner(System.in);
    do {
        System.out.print("Price: $");
        price = input.nextDouble();
        System.out.print("From: $");
        pay = input.nextDouble();
        change = pay - price;


        twenty =  (int) (change / 20.00);
        rem =  (int) (change % 20.00);
        ten =  (int) (rem / 10.00);
        rem =  (int) (rem % 10.00);
        five =  (int) (rem / 5.00);
        rem =  (int) (rem % 5.00);
        one =  (int) (rem);
        //
        qs = (int) rem / 25;
        rem = (int) rem % 25;
        ds = (int) rem / 10;
        rem = (int) rem % 10;
        ns = (int) rem / 5;
        rem = (int) rem % 5;
        ps = (int) rem;
        System.out.println("Computed change: $" + change);
        System.out.println(twenty + " x $20 bills, \n" + ten
                + " x $10 bills, \n" + five + " x $5 bills, \n" + one
                + " x $1 bills, \n" + qs + " x 25c coins \n" + ds
                + " x 10c coins \n" + ns + " x 5c coins \n" + ps
                + " x 1c coins \n");

        System.out.println("Would you like to enter another "
                + "quantity? (Y or N):");
        input.nextLine();
        user = input.nextLine();

        if (!user.equalsIgnoreCase("y")) {
            System.out.println("Goodbye!");
        }
    } while (user.equalsIgnoreCase("y"));
    input.close();
    // System.exit(0);

I'm almost sure the problem lies in casting the value of the remainder as an int, which would discard any value after the decimal point. I've tried dividng and modulo operation with .25, .10, .5, .1 but that doesn't seem to work. There is something I'm not seeing.

Before we go on: http://stackoverflow.com/questions/3730019/why-not-use-double-or-float-to-represent-currency — John3136, Feb 11 '15 at 02:17
you can use BigDecimal instead of double and use remainder.. — nachokk, Feb 11 '15 at 02:21
Thanks, really helpful link as well as @nachokk comment. Really appreciate it. — , Feb 11 '15 at 02:30

score 1 · Answer 1 · answered Feb 11 '15 at 02:18

1

Compute the price in cents, this way you can avoid using decimal places.

answered Feb 11 '15 at 02:18

StenSoft

9,369
25
30

score 0 · Answer 2 · answered Feb 11 '15 at 02:24

0

You should not use double or float for currency as their precision is not perfect. You might want to convert the entire number as a Long representing the cents, then format to output the decimal. That way, your math calculus will be decimal free.

Something like

Long price = Long.parseLong(input.nextLine().replace(",", ""));
NumberFormat n = NumberFormat.getCurrencyInstance(Locale.US); 
String s = n.format(price / 100.0);
System.out.println(s);

Now, you should be able to easily resolve your issue.

answered Feb 11 '15 at 02:24

Jean-François Savard

20,626
7
49
76

Would you say using long is a quicker way to write the program. Or should I consider using the BigDecimal class instead? – Feb 11 '15 at 02:29
1

@LuisFelipe I would still prefer using `Long` as it will be easier for you if you have any math to do on the value. – Jean-François Savard Feb 11 '15 at 02:47
@LuisFelipe I got no feedback, did this answer works for you ? – Jean-François Savard Feb 11 '15 at 20:11

Decimal Value error

2 Answers2