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Java Java Objects Delivering the MVP Applying a Discount Code

Posted by Luis Flores
Luis Flores
10,499 Points

|| vs &&

the challenge is

"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."

there seems to be a split in the forums in which way is correct (|| or &&)

iv'e tried both methods and both gave me the correct answer but i feel like the || is the proper 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;
  }

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



  private String normalizeDiscountCode(String discountCode){
    for (char c : discountCode.toCharArray()){  
      if (!Character.isLetter(c) && c != '$'){         
        throw new IllegalArgumentException("Invalid discount code"); 
      }
    }
    discountCode = discountCode.toUpperCase();
    return discountCode;
  }
}
 // second method is under

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

Lukas Dahlberg
Lukas Dahlberg
53,736 Points

In this case the && is preferable because of readability. The result of !( expression1 || expression2 ) is far harder to grasp, especially when reading large of chunks of code, than !expression && !expression is. (I'm a professional Java dev, and it took me a couple minutes to see the placement of the parentheses.) In general, keep code as simple and elegant as possible instead of relying on logical gymnastics because it'll reduce the number of bugs and logic errors in your code. Both because you would easily miss the || during personal code reviews and because others might as well . Plus the && has the added benefit of reading more like the original problem statement.

Luis Flores
Luis Flores
10,499 Points

thank you