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Java Java Objects Delivering the MVP Applying a Discount Code

Moe Shanti
Moe Shanti
519 Points

What is wrong with my code

Hi, the message i am given when i run this code: Illegal argument Exeception"invalid..." look around line 15

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){
    for( char c : discountCode.toCharArray())
    { 

      if (!Character.isLetter(c) || c != '$'){
     throw new IllegalArgumentException ("Invalid discount code");

    }

    }
   discountCode = discountCode.toUpperCase();
    return discountCode;
  }

  public String getItemName() {
    return itemName;
  }

  public int getPriceInCents() {
    return priceInCents;
  }

  public String getDiscountCode() {
    return discountCode;
  }

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

Graham Huelscher
Graham Huelscher
7,003 Points

Hi Moe,

The issue lies with your if statement here:

if (!Character.isLetter(c) || c != '$'){ throw new IllegalArgumentException ("Invalid discount code");

Since you are using the OR operator, when the character variable "c" is not the '$', the if statement evaluates to true and the exception is thrown.

For example: c = a.

We'll look at the overall if statement piece by piece

if (!Character.isLetter(c) || c != '$')


!Character.isLetter(c) => false, since 'a' is a letter.

c != '$' => true, since 'a' != '$'.

Therefore the if statement is:

if(false || true)

which proceeds into the if statement code and the exception is thrown.

Hope that helped!