Normalizing Discount Code results in Task 1 no longer working.

Question

As far as I can tell, I'm executing this properly. Task 1 was of course working before the introduction to the dollar sign. The ability to debug being limited, I get the code to run but the result is "Oops! It looks like Task 1 is no longer working".

Can anybody spot a flaw here?

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

    return discountCode;
  }

  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"
    }

  }
}

Answer 1 · 2017-01-16T21:02:54Z

January 16, 2017 9:02pm

Heya Jonathan

All is good with your code, there is a small mishap though, your not sign(!) should be either right next tot the Character.isLetter(), or just encapsulate the whole statement and make it not letter nor a dollar sign and all will work like a charm

private String normalizeDiscountCode(String discountCode){
    discountCode = discountCode.toUpperCase();
    for (char letter : discountCode.toCharArray()){
      if ( ! Character.isLetter(letter) ||  letter != '$' ){ // your not sign (!) should enclose both statements
        throw new IllegalArgumentException("Invalid discount code.");
      }
    }

    return discountCode;
  }

Good luck !

-Alex

Answer 2 · 2017-01-16T20:59:26Z

January 16, 2017 8:59pm

There is a flaw in your code, but it's a very common flaw for this task. Probably because of how the task is phrased.

To illustrate the flaw I'll walk through what will happen with your application when a discount code is passed in. Let's say the discount code is F$L which is a valid code and should not throw an error.

First your code will check if F is not a letter, since it is a letter this will be false, then it will check if it is not $. Since F is in fact not $ this condition will be true. Since you use the OR (||) operator your if statement will run as long as one of the conditions is true. F will therefore cause the if statement to run which will trigger the exception. Even though F is in fact a valid character. The same sort of error occurs with $ except that the first condition is true while the second is false.

There are multiple ways of avoiding this issue but the simplest is probably to change the || operator to &&. && will only return true if both of the conditions are true, which is the behavior you actually want from the if statement you have written.

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Jonathan Mitten

Jonathan Mitten

Normalizing Discount Code results in Task 1 no longer working.

2 Answers

Alex Bratkovskij

Alex Bratkovskij

andren

andren