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Java Java Objects Delivering the MVP Applying a Discount Code

what's the logic ?

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.

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;
  }

  private String normalizeDiscountCode(String discountCode){
    if(!discountCode.matches("[a-zA-Z]+")|| !discountCode.matches('$'){
    throw new IllegalArgumentException("Invalid Discount Code");
    }
  discountCode = discountCode.toUpperCase();
    return discountCode;
  }

  public int getPriceInCents() {
    return priceInCents;
  }

  public String getDiscountCode() {
    return discountCode;
  }

  public void applyDiscountCode(String discountCode) {
    discountCode = normalizeDiscountCode(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"
    }

  }
}

2 Answers

Thomas Nilsen
Thomas Nilsen
14,957 Points

Try this instead;

private String normalizeDiscountCode(String discountCode){
        //Loop through the passed in String
        for(char c : discountCode.toCharArray()) {
            //For each letter, we check if the
            //character is NOT a letter, and at the same time is not
            //a dollar-sign either - we throw an exception
            if(!Character.isLetter(c) && c != '$') {
                throw new IllegalArgumentException("invalid discount code.");
            }
        }

        //return the valid code
        return discountCode.toUpperCase();
    }

Thank you Thomas Nilsen.