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Java Java Objects Delivering the MVP Applying a Discount Code

Java Objects - Applying a discount code Pt.2 - I do not understand how to do this. Please help!


Let's use your normalization skills to normalize a discount code for a Shopping Cart application. All codes should be upper cased, no matter what the user enters

For this first task, create a new private method named normalizeDiscountCode. It should take the discount code that is passed into the method and return the uppercase version. Call it from the current applyDiscountCode method and set this.discountCode to the result.


./Order.java:23: error: cannot find symbol if (! discountCode.isLetter(discountCode)) { ^ symbol: method isLetter(String) location: variable discountCode of type String Note: JavaTester.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

I do not understand what to do here. I know I should get rid of isLetter but I don't see any other ways besides of doing

if (! "A", "B", "C", "D", "E", "F", "G", "H", "I", ............ "X", "Y", "Z"(discountCode)) { throw new IllegalArgumentException("Invalid discount code."); }

And I also have to put the dollar sign with it some where. But do I do it by doing "$"?

public class Order {
  private String itemName;
  private int priceInCents;
  private String discountCode;

  public Order(String itemName, int priceInCents) {
    this.itemName = itemName;
    this.priceInCents = priceInCents;

  public String getItemName() {
    return itemName;

  public int getPriceInCents() {
    return priceInCents;

  public String getDiscountCode() {
    return discountCode;
  private String normalizeDiscountCode(String discountCode) {
    if (! discountCode.isLetter(discountCode)) {
      throw new IllegalArgumentException("Invalid discount code.");
    return discountCode.toUpperCase();
  public void applyDiscountCode(String discountCode) {
    this.discountCode = normalizeDiscountCode(discountCode);
public class Example {

  public static void main(String[] args) {
    // This is here just for example use cases.

    Order order = new Order(
            "Yoda PEZ Dispenser",

    // These are valid.  They are letters and the $ character only
    order.getDiscountCode(); // ABC

    order.getDiscountCode(); // $ALE

    try {
      // This will throw an exception because it contains numbers
    } catch (IllegalArgumentException iae) {
      System.out.println(iae.getMessage());  // Prints "Invalid discount code"
    try {
      // This will throw as well, because it contains a symbol.
    }catch (IllegalArgumentException iae) {
      System.out.println(iae.getMessage());  // Prints "Invalid discount code"


2 Answers

Daniel Turato
.a{fill-rule:evenodd;}techdegree seal-36
Daniel Turato
Java Web Development Techdegree Graduate 30,124 Points

Here's how I did it:

private String normalizeDiscountCode(String discountCode) {
    for (char c : discountCode.toCharArray()) {
      if (!(Character.isLetter(c) || c == '$' )) {
        throw new IllegalArgumentException("Invalid discount code");

    return discountCode.toUpperCase();

So in the challenge, you need to make sure each character is either a letter or is equal to a $ character. To do this you need to loop over each character in the discountCode which I used a for loop. And to be able to loop through the discountCode, I had to convert the discountCode into a char array. Then at each iteration, i used an if statement to check if that particular letter was a letter or equal to $ and if false, threw the IllegalArgumentException. Hopefully this helps

Thanks a lot! Your explanation really helped a lot!