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Java Java Objects Delivering the MVP Applying a Discount Code

Hieu Mai
Hieu Mai
8,792 Points

I can not do the second part of this quiz!!!

for (char c : discountCode.toCharArray()){ if(!Character.isLetter(c) || c != '$'){ throw new IllegalArgumentException("Invalid discount code"); }
} return discountCode.toUpperCase();

Order.java
public class Order {
  private String itemName;
  private int priceInCents;
  private String discountCode;
  private String normalizeDiscountCode(String discountCode){
    for (char c : discountCode.toCharArray()){
      if(!Character.isLetter(c) || c != '$'){
        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

Simon Coates
Simon Coates
28,693 Points
  private String normalizeDiscountCode(String discountCode){
    for (char c : discountCode.toCharArray()){
      if(!Character.isLetter(c) && c != '$'){
        throw new IllegalArgumentException("Invalid discount code");
      }  
    }
    return discountCode.toUpperCase();
  }

validity is when it's a letter OR $. Not being valid is thus !(letter or $). !(letter or $) evaluates to (!letter && !$). It's a rule regarding logic within maths. (see https://en.wikipedia.org/wiki/De_Morgan%27s_laws . keep in mind that maths doesn't usually use ! for negation.)