Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Java Java Objects Delivering the MVP Applying a Discount Code

Chris Mitts
Chris Mitts
855 Points
Posted by Chris Mitts
Chris Mitts
855 Points

Solution to Task 2 nullifies Task 1

I am attempting to solve this objective by turning my Discount Code string into a char array and checking each character in that char array. If the character in the char array is not a letter or $ then I throw the exception. When I check my work I get the error that now my Task 1 is no longer working and I am not sure why. Thank you for your help

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;
  }

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

  }
}

1 Answer

andren
andren
28,558 Points
andren
andren
28,558 Points

The problem is that your code raises an exception for discount codes that are valid. In fact it actually raises an exception for all discount codes, and that's why task 1 is no longer passing.

You check if a character is not the $ symbol OR not a letter, that means that an exception will be raised if either of those conditions are true. Let's say the character in question was 'A' that is a letter so the second condition would be false, but 'A' is not the $ symbol so the first condition would be true, which means that an exception would be thrown. Even though 'A' is a valid letter for the discount code.

The same type of thing would happen if the character was $, since that is not a letter.

The easiest way around this is to replace || (OR) with && (AND), that way an exception is only thrown if the character is both not a letter AND not the $ symbol. Like this:

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;
  }

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

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

Edit: Changed my wording a bit.

Chris Mitts
Chris Mitts
855 Points
Chris Mitts
Chris Mitts
855 Points

Appreciate the help, got my logic confused there, thank you!