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Java Java Objects Delivering the MVP Applying a Discount Code

Olha Markova
Olha Markova
2,050 Points

Problem with a normalize method

I am working at the challenge "Applying a Discount Code" and get an error message, when I am trying to use normilize method

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){
  this.discountCode = normalizeDiscountCode (discountCode);
  return (discountCode.toUpperCase());
      }

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

  }
}
Simon Coates
Simon Coates
28,694 Points

with your code, the following function is recursive.

  private String normalizeDiscountCode (String discountCode){
  this.discountCode = normalizeDiscountCode (discountCode);
  return (discountCode.toUpperCase());
      }

If you call this method, it calls itself, which calls itself, which calls itself. Sometimes this is what you want to do, but typically only if there is a condition being applied that can stop further recursive calls. The wiki article on recursive states:

"Recursion occurs when a thing is defined in terms of itself or of its type. Recursion is used in a variety of disciplines ranging from linguistics to logic. The most common application of recursion is in mathematics and computer science, where a function being defined is applied within its own definition. While this apparently defines an infinite number of instances, it is often done in such a way that no loop or infinite chain of references can occur."

1 Answer

Simon Coates
Simon Coates
28,694 Points

You have most of the right bits of code, just in the wrong places. Try

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

  private String normalizeDiscountCode(String discountCode){
    return discountCode.toUpperCase();
  }