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Java Java Objects Delivering the MVP Applying a Discount Code

Amir Tamim
Amir Tamim
8,597 Points

Please help! Been stuck all day

I have to say I kinda give up on this one. Can someone please give the logic behind the answer to this and correct my errors?

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){

    if(discountCode.indexOf(discountCode)!=-1){
      throw new IllegalArgumentException("Invalid discount code.");
    }
    return discountCode.toUpperCase(); 
  }
}
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"
    }

  }
}
Amir Tamim
Amir Tamim
8,597 Points

QUESTION IS:

In the normalizeDiscountCode verify that only letters or the $ character are used. If any other character is used, throw a IllegalArgumentException with the message Invalid discount code.

2 Answers

Felix Sonnenholzer
Felix Sonnenholzer
14,654 Points

Hi there,

You have to check every char in that String. So you would have to loop over every char to check.

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

Just for explanation if

  • c is a letter it returns true -> thanks to ! it will be false and won't throw an Exception
  • c is not a letter -> check if c is a $
    • c is a $ it returns true -> thanks to ! it will be false and won't throw an Exception
    • c is not $ it returns false -> thanks to ! it will be true and will throw an Exception

I hope I expressed it easy to understand.

Have fun

Christopher Ekeren
Christopher Ekeren
1,370 Points

Thank you for this! I was struggling mightily on this. I actually started using the toCharArray approach but figured I was just overcomplicating it. Apparently I was on the right track, I should have just stuck with it lol.