Design a cash register program


Your register currently has the following bills/coins within it:

'PENNY': .01,

'NICKEL': .05,

'DIME': .10,

'QUARTER': .25,


'ONE': 1.00,

'TWO': 2.00,

'FIVE': 5.00,

'TEN': 10.00,

'TWENTY': 20.00,

'FIFTY': 50.00,

'ONE HUNDRED': 100.00

Your program should accept as its first argument a path to a filename. The input file contains several lines. Each line is one test case. Each line contains two numbers which are separated by a semicolon. The first is the Purchase price (PP) and the second is the cash(CH).

For each set of input produce a single line of output, which is the cashBack to be returned to the customer. In case the CH < PP, print out ERROR. If CH == PP, print out ZERO. For all other cases print the amount that needs to be returned, in terms of the currency values provided. The output should be sorted in highest-to-lowest order


import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class CashRegister {
    public static void main(String[] args) throws FileNotFoundException {
        File file = new File(args[0]);
        Scanner fileInput = new Scanner(file);

        while (fileInput.hasNextLine()) {

    private static void printCashChange(String line) {
        float pp = Float.parseFloat(line.split(";")[0]);
        float ch = Float.parseFloat(line.split(";")[1]);

        System.out.println(getCashChange(pp, ch));

    private static String getCashChange(float price, float cash) {
        if (cash < price) { return "ERROR"; }
        if (cash == price) { return "ZERO"; }
        float cashBack = cash - price;

        StringBuilder change = new StringBuilder();

        while (cashBack > 0.01f) {
            if (cashBack >= 100.0f) {
                change.append("ONE HUNDRED");
                cashBack -= 100.0f;
            } else if (cashBack >= 50.0f) {
                cashBack -= 50.0f;
            } else if (cashBack >= 20.0f) {
                cashBack -= 20.0f;
            } else if (cashBack >= 10.0f) {
                cashBack -= 10.0f;
            } else if (cashBack >= 5.0f) {
                cashBack -= 5.0f;
            } else if (cashBack >= 2.0f) {
                cashBack -= 2.0f;
            } else if (cashBack >= 1.0f) {
                cashBack -= 1.0f;
            } else if (cashBack >= 0.5f) {
                change.append("HALF DOLLAR");
                cashBack -= 0.5f;
            } else if (cashBack >= 0.25f) {
                cashBack -= 0.25f;
            } else if (cashBack >= 0.1f) {
                cashBack -= 0.1f;
            } else if (cashBack >= 0.05f) {
                cashBack -= 0.05f;
            } else {
                cashBack -= 0.01f;
        change.setLength(change.length() - 1);

        return change.toString();

Every now and then one creates a solution that works but really comes off as sub-optimal, this is one of those times for this CRer. It really seems verbose, I'd appreciate any tips on improving performance and general structure.


1 Answer 1


For convenience, even though the challenge doesn't specify it, I suggest optionally taking input from System.in. It's more reasonable behaviour than crashing with an ArrayIndexOutOfBoundsException.

Scanner input = (args.length > 0) ? new Scanner(new File(args[0]))
                                  : new Scanner(System.in);

In printCashChange(), avoid two calls to split().

String[] fields = line.split(";", 2);
float pp = Float.parseFloat(fields[0]);
float ch = Float.parseFloat(fields[1]);

The loop in getCashChange() should be data-driven, like this:

for (Denomination d : Denomination.values()) {
    while (cashBack >= d.getValue()) {
        cashBack -= d.getValue();

Here's an enum to support that:

public enum Denomination {
          FIFTY( 50.00f),
         TWENTY( 20.00f),
            TEN( 10.00f),
           FIVE(  5.00f),
            TWO(  2.00f),
            ONE(  1.00f),
    HALF_DOLLAR(  0.50f),
        QUARTER(  0.25f),
           DIME(  0.10f),
         NICKEL(  0.05f),
          PENNY(  0.01f);

    private final float value;
    private final String description;

    Denomination(float value) {
        this.value = value;
        this.description = this.name().replace("_", " ");

    public float getValue() {
        return this.value;

    public String toString() {
        return this.description;

The performance of your program will be fine. You aren't doing anything particularly inefficient, and the bottleneck will be I/O rather than processing.

  • 1
    \$\begingroup\$ This part is clever: for (Denomination d : Denomination.values()) { while (cashBack >= d.getValue()) { ... }. One more thing, how do you ensure that always the bigger value will get substracted first? \$\endgroup\$
    – yadav_vi
    Jan 20, 2015 at 6:37
  • 1
  • \$\begingroup\$ I would really like to know how you approach the code. For e.g. I would never have come up with something like this - Denomination(float value) { ... this.description = this.name().replace("_", " "); ...} and then using it as public String toString() { return this.description; } and finally as change.append(d).append(',');. If you have a git repo for the code, please post it here too. \$\endgroup\$
    – yadav_vi
    Jan 20, 2015 at 19:01

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