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Java Java Objects Delivering the MVP Applying a Discount Code

M Costa
M Costa
1,621 Points

Question on the below task: "In the normalizeDiscountCode verify that only letters or the $ character are used."

I've already passed this task using '&&' but can someone explain why I can't use '||' as listed below?

I get the error 'Bummer: java.lang.IllegalArgumentException': ABC must only contain letters or '$' signs (Look around Order.java line 19)

Also I couldn't tell if this was my throw exception or a java error.

Much appreciated!

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 discount){
    discountCode = discountCode.toUpperCase();  
    discount = discountCode;

//  char[] discountChar = discount.toCharArray();

    for(char discountChar : discount.toCharArray()){

        if (! Character.isLetter(discountChar) || discountChar !='$'){
            throw new IllegalArgumentException(discount + " must only contain letters or '$' signs");
        }   
    } return discount;
  }
  public String getItemName() {
    return itemName;
  }

  public int getPriceInCents() {
    return priceInCents;
  }

  public String getDiscountCode() {
    return discountCode;
  }

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

  }
}

1 Answer

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

The challenge states that the discount has to be a letter or contain the $ character. Therefore, to check for a failure on this occurrence it can NOT be a letter or contain the $ symbol. What you did was that it can't be a letter or it can't be equal to the $ character meaning even if a non letter was passed in the discount code, it would still pass through the if statement as its not equal to '$' resulting in true for the OR logic. Here is the correct code by using OR:

if (!(Character.isLetter(discountChar) || discountChar == '$')) {
    throw new IllegalArgumentException(discount + " must only contain letters or '$' signs");
}