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Java Java Objects Delivering the MVP Applying a Discount Code

sabath rodriguez
sabath rodriguez
11,055 Points
Posted by sabath rodriguez
sabath rodriguez
11,055 Points

I know that theres something wrong with the way I'm checking discountCode, but I can't figure out the right one.

private String normalizeDiscountCode(String discountCode) { for (char discountCodeLetters : discountCode.toCharArray()) { if (discountCode.contains(discountCodeLetters) == ("[a-zA-Z]+") || discountCode.indexOf(discountCodeLetters) == ('$')) { return discountCode.toUpperCase(); } else { throw new IllegalArgumentException("invalid discount code!"); } } }

Order.java 
public class Order {
  private String itemName;
  private int priceInCents;
  private String discountCode;

  private String normalizeDiscountCode(String discountCode) {
   if (discountCode.matches("[a-zA-Z]+") || discountCode.('$')) {
       return discountCode.toUpperCase();
    } else {
     throw new IllegalArgumentException("invalid discount code!");
   }
  }

  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);
  }
}
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

Your code is quite close, but there are some issues both code wise and logic wise.

Code wise you have forgotten to write matches in your second condition to the if statement. You are also passing in a char rather than a string due to using single quotes rather than double quotes. The matches function requires that you pass it a string.

But even if you fix that your function will still fail because the two regex patterns will be evaluated independently. It will first check if the code only contain letters, then if that is not the case it will check if it only contains the $ symbol. If a discount code is passed that contains both letters and the $ symbol then both of those regex patterns will fail and an exception will be raised.

The way around that is to combine the two regex patterns into one, which is actually quite simple to do. Just place the $ symbol within the brackets of your first pattern like this:

public class Order {
  private String itemName;
  private int priceInCents;
  private String discountCode;

  private String normalizeDiscountCode(String discountCode) {
    if (discountCode.matches("[a-zA-Z$]+")) {
      return discountCode.toUpperCase();
    } else {
      throw new IllegalArgumentException("invalid discount code!");
    }
  }

  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);
  }
}

That way the regex pattern will match any character between a-z/A-Z and the $ symbol, only symbols other than those will not match.