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Java Java Objects Delivering the MVP Applying a Discount Code

I don't understand why my normlizeDicountCode does not work when it try to check if it not a letter and if it not '$'.

In other words, I'm trying to determine if the String passed through to normlizeDicountCode is a letter or $ if not then throw new IllegalArgumentException (You know the drill). However, its seems not to work, but I don't know why can anyone tell me what went wrong? Thanks!

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

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

  private String normalizeDiscountCode(String discountCode) {
    try {
      for (int i = 0; i < discountCode.length(); i++) {
        if (!Character.isLetter(discountCode.charAt(i)) && discountCode.indexOf('$') != -1) {
            throw new IllegalArgumentException("Invalid discount code.");        
        }
      }
    } catch (IllegalArgumentException iae) {
      System.out.println(iae.getMessage());
    }

    return discountCode.toUpperCase();
  }

  public String getItemName() {
    return itemName;
  }

  public int getPriceInCents() {
    return priceInCents;
  }

  public String getDiscountCode() {
    return discountCode;
  }

  public void applyDiscountCode(String discountCode) {
    this.discountCode = normalizeDiscountCode(discountCode);
  }
}
Example.java
public class Example {

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

    Order order = new Order(
            "Yoda PEZ Dispenser",
            600);

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

    order.applyDiscountCode("$ale");
    order.getDiscountCode(); // $ALE


    try {
      // This will throw an exception because it contains numbers
      order.applyDiscountCode("ABC123");
    } catch (IllegalArgumentException iae) {
      System.out.println(iae.getMessage());  // Prints "Invalid discount code"
    }
    try {
      // This will throw as well, because it contains a symbol.
      order.applyDiscountCode("w@w");
    }catch (IllegalArgumentException iae) {
      System.out.println(iae.getMessage());  // Prints "Invalid discount code"
    }

  }
}

2 Answers

Umesh Ravji
Umesh Ravji
42,386 Points

Hi Kamil, there's a minor issue with your conditional check, and in this question the method is supposed to just throw the exception. Don't handle the IllegalArgumentException in your method.

if (!Character.isLetter(discountCode.charAt(i)) && discountCode.indexOf('$') != -1) {
     throw new IllegalArgumentException("Invalid discount code.");        
}

Bummer! Hmmm...I ran order.applyDiscountCode("h1!") and I expected it to throw an IllegalArgumentException, but it didn't

Using that as my example, the problem is that your conditional check will only throw an IllegalArgumentException when the character is not a letter and there a $ in the discountCode. So, when it gets to the 1, the first condition is true, but the second one is not.

if (!Character.isLetter(discountCode.charAt(i)) && discountCode.charAt(i) != '$') {
    throw new IllegalArgumentException("Invalid discount code.");
}

Here, the first conditional check on the 1 is true, and the secound check is also true because the character is not a $. Exception gets thrown. It looks like you were trying to do it this way, but just didn't have the right condition.

Elling Hauge
Elling Hauge
6,383 Points

I tested your code and it works for me. Both order.applyDiscountCode("w@w"); order.applyDiscountCode("ABC123"); throws back Invalid discount code.

But for some reason the tester is not accepting it, any guesses why?