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Java Java Objects Delivering the MVP Applying a Discount Code

What did I do wrong?

I don't really understand what I did wrong here Can someone please explain? It says: "Bummer: java.lang.IllegalArgumentException: Invalid discount code (Look around Order.java line 31)"

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 String getItemName() {
    return itemName;
  }

  public int getPriceInCents() {
    return priceInCents;
  }

  public String getDiscountCode() {
    return discountCode;
  }

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

  private String normalizeDiscountCode(String discountCode) { 

    for ( char letter : discountCode.toCharArray() ) {
        if ( !(Character.isLetter(letter)) || !(letter == '$') ) {
          throw new IllegalArgumentException("Invalid discount code"); 
        }
    }
    discountCode = discountCode.toUpperCase();
    return 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

Simon Coates
Simon Coates
4,968 Points

I think you've incorrectly applied demorgan's law. It seems to accept

private String normalizeDiscountCode(String discountCode) { 

    for (char letter : discountCode.toCharArray() ) {
        if ( !Character.isLetter(letter) && letter != '$' ) {
          throw new IllegalArgumentException("Invalid discount code."); 
        }
    }
    return discountCode.toUpperCase();
   }

A character is valid if it's a letter OR it's a $. To invert things, it becomes if not a letter AND not a $. (In honesty, a lot of people trip over this one. There are 14 pages of community questions for that challenge. I've written that code at least 10 times and I still have to think about the conditions)

Thank you!