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Java Java Objects Delivering the MVP Applying a Discount Code

Damjan Vlaic
Damjan Vlaic
19,244 Points
Posted by Damjan Vlaic
Damjan Vlaic
19,244 Points

---JAVA---

can someone help me with this if statement in the last method pls :)

In the normalizeDiscountCode verify that only letters or the $ character are used. If any other character is used, throw a IllegalArgumentException with the message Invalid discount code.

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;
  }

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

  private String normalizeDiscountCode(String discountCode) {
    return discountCode.toUpperCase();
    if (! discountCode.isLetter() || ! '$') {
      throw new IllegalArgumentException("Invalid discount code.");
    }
  }
}

2 Answers

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Hi there,

For starters, you have returned out of the method before applying the condition; make the return statement the last line of the method.

Next, you need something to compare with ! - you need to break the discountCode down into an array then iterate over that in a for loop. At each loop, you test each character to see if it is/isn't a letter and is/isn't a dollar sign. Depending on that, throw the exception or not. Note that you have to stipulate both tests in full - one, you have correctly established, is using the isLetter() method - however, this can't be called on a String - it is a class method of the Character class.

So, some steps:

  • First - convert the incoming discountCode into an array of characters.
  • Second - loop over that array, one character at a time.
  • Third - test each character to see if it is a letter (isLetter() will help here); test it against for being a dollar sign - watch your logic!

Depending on the logic used, throw the exception or return the uppercase discountCode.

Let me know how you get on.

Steve.

P.S. You can also use a regular expression to solve this in fewer steps.

Damjan Vlaic
Damjan Vlaic
19,244 Points
Damjan Vlaic
Damjan Vlaic
19,244 Points

everything you told me helped me a lot but still trying to write that if statement correctly, can you help me with it pls :)

here's my code (method)

  private String normalizeDiscountCode(String discountCode) {
    for (char letter : discountCode.toCharArray()) {
      if (letter != letter.isLetter() || letter != '$') {
      } throw new IllegalArgumentException("Invalid discount code.");
    }
    return discountCode.toUpperCase();
  }
Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Two issues there that I can see, and I'm on my phone about to go to sleep.

First, as in my earlier post, the isLetter method is a class method of the Character class. Read up on how to use it.

Second, your logic in your test is wrong. You want see if the letter is not a letter AND is not a dollar sign. The negation makes an OR unworkable. Think that through.

Steve.

Damjan Vlaic
Damjan Vlaic
19,244 Points
Damjan Vlaic
Damjan Vlaic
19,244 Points

i have solved it. I wrote ! Character.isLetter(letter) && letter != '$' tnx for helping me steve ;)

Steve Hunter
Steve Hunter
57,712 Points

Good work! :+1: