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Java Java Objects Delivering the MVP Applying a Discount Code

I am getting an error on this but I am not sure what it is. Any ideas?

This question is giving me an error on the order. Don't know how to fix it.

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 code) {
    String result = code.toUpperCase();
    for (char letter : result.toCharArray()) {
      if (letter != '$' || !Character.isDigit(letter) || !Character.isLetter(letter)) {
        throw new IllegalArgumentException("Invalid Discount Code");
      }
    }
    return result;
  }
}
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

Steven Parker
Steven Parker
218,583 Points

When checking for "not" something, the tests must be combined with and operations instead of or. No matter what the item is, it will always "not be" most of the conditions:

//          not a $     AND       not a digit         AND        not a letter
      if (letter != '$' && !Character.isDigit(letter) && !Character.isLetter(letter)) {

Another approach would be to combine the tests for what it can be first, then negate the entire thing:

//        NOT (    a $       OR        a digit          OR         a letter    )
      if ( !(letter == '$' || Character.isDigit(letter) || Character.isLetter(letter)) ) {