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Java Java Objects Delivering the MVP Applying a Discount Code

Issues with method to normalize String.

I'm not entirely sure what to even ask here. In the lesson we are working with a method that returns a char. The method in this exercise returns a String. I've gone to Oracle's website and I have tried to find resources. I thought the following would give me what I want because I am testing if it is not a unicode character or if it is not containing a $ symbol, then we will throw the exception.

if (! discountCode.charAt() || ! discountCode.contains('$') {
     throw new IllegalArgumentException("blah blah");
}

Again I don't really know what to even ask.

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

  private String normalizeDiscountCode(String discountCode) {
    if (! discountCode.charAt() || ! discountCode.contains('$')) {
      throw new IllegalArgumentException("Invalid discount code.");
    }
    return discountCode.toUpperCase();
  }

  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

Fatemah Tavakoli
Fatemah Tavakoli
13,797 Points

Hi,

The question is asking to loop through the discountCode and make sure that there are only letters or '$' character. the problem comes with "discountCode.charAt()". Java String charAt() method returns the character at the specified index, which is not asked by the question. To solve it we should turn our discountCode string Into array of char and check if it meets the conditions. To get this array we use ".ToCharArray()" method.

private String normalizeDiscountCode(String discountCode) {
    //looping through the array
    for (char codeChar:discountCode.toCharArray()){
      //checking the conditions
      if ( !Character.isLetter(codeChar) && codeChar != '$'){
        throw new IllegalArgumentException("Invalid discount code"); 
      }
    }
    return discountCode.toUpperCase(); 
  }

Hope it helps! :)

Thank you!