Java cash register: Getting change from in different subunits

Question

Teaching myself Java, I reached an example problem that asks me to create a cash register program that will calculate the total change back to the customer in Dollars, Nickels, Quarters, Dimes, and pennies.

I worked out the user input but getting the correct sub-units is tricky part. For example: it's was easy to write the line of code that returned $1 dollar back if the cost was $4 and amount tendered was $5. But the trouble I am having is putting how many dimes and pennies needed in the correct field. ex2: total cost $4.62, tendered: $5, change: $0.38

            System.out.print("Enter the sale amount: $   ");
    double sale = user.nextDouble();
    System.out.print("Enter the amount tendered by customer: $   ");
    double tendered = user.nextDouble();
    double totalChange = (tendered - sale);
    System.out.printf("TOTAL CHANGE: $  %.2f\n", totalChange);
    dollars = totalChange/1;
    quarters = totalChange/25;
    dimes = totalChange/10;
    nickels = totalChange/5;
    pennies = totalChange/1;




    System.out.printf("DOLLARS: %.2f\n", dollars);
    System.out.printf("QUARTERS: %.2f\n", quarters);
    System.out.printf("DIMES: %.2f\n", dimes);
    System.out.printf("NICKELS: %.2f\n", nickels);
    System.out.printf("PENNIES: %.2f\n", pennies);

I don't need the answer (because I want to learn and teach myself), but just need some advice on how to go about doing so.

EDIT: What am I doing wrong with this algorithm:

            dollars = totalChange/1;
    dollars = (int)dollars;
    dl = totalChange % 1;

    quarters = dl/0.25;
    q = quarters % 0.25;
    quarters = (int)quarters;

    dimes = q / .10;
    d = dimes % .10;



    nickels = d / .5;
    n = nickels % .5;

    pennies = n / .1;
    n = pennies/ .1;

It would be good to work with BigDecimal as well instead of doubles and ints. See this stackoverflow question: http://stackoverflow.com/questions/1359817/using-bigdecimal-to-work-with-currencies — mdewitt, Jan 28 '14 at 23:35
will do! I did learn about the NumberFormat class. Should I figure out the algorithm first? Or will changing data types complicate it? — Joseph, Jan 28 '14 at 23:37
It is going to be more work to code it one way, and then have to go back and switch the data types. But, in this case, I think it is best to get a good understanding of the algorithm first because you are teaching yourself Java. — mdewitt, Jan 28 '14 at 23:41
I wouldn't switch to BigDecimal yet. Not until you've worked out the logic. But I would switch to using int, or long, and working with whole numbers of cents. Using floating point for money is just going to cause problems. — David Conrad, Jan 29 '14 at 00:05

score 1 · Answer 1 · answered Jan 28 '14 at 23:33

1

You are on the right track. After determining the largest number of whole dollars in change, subtract it. Then determine the largest number of quarters you can get from what is left. Repeat for each. It's the same way you do it yourself as a human.

answered Jan 28 '14 at 23:33

Teresa Carrigan

658
7
14

Java cash register: Getting change from in different subunits

1 Answers1