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Java Java Objects Delivering the MVP Applying a Discount Code

Jack Cummins
Jack Cummins
17,417 Points
Posted by Jack Cummins
Jack Cummins
17,417 Points

@stevehunter Please help me with this.

Steve Hunter please help me

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

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


}

2 Answers

Steve Hunter
Steve Hunter
57,712 Points

Only just saw this; sorry, Jack Cummins.

You've got an answer, so you're good to go! However, there's a slightly more elegant way of testing if a char is a letter. The Character class has a class helper method called isLetter() which returns true or false depending whether the passed-in char is a letter. To use a class method, chain it to the class itself using dot notation.

So, you end up with something like:

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

There's an issue with the other solution as it requires the discountCode to be made up of upper case letters. Testing (c >= 'A' && c <= 'Z') doesn't help with lowercase letters. You could do this:

(Character.toUpperCase(c) >= 'A' && Character.toUpperCase(c) <= 'Z')

But that's getting ugly - I'd recommend the use of the .isLetter() method for its better handling of cases, and overall clarity.

I hope that makes sense.

Steve.

Steve Hunter
Steve Hunter
57,712 Points

You could send the discountCode to upper case prior to the testing to alleviate this issue. But the code still lacks the clarity of using the helper method:

  private String normalizeDiscountCode(String discountCode){
    discountCode = discountCode.toUpperCase();
    for (char c: discountCode.toCharArray()){
      if ( !((c >= 'A' && c <= 'Z') || c == '$') ){
             throw new IllegalArgumentException("Invalid discount code");
      }
    }
    return discountCode;
  }
Jack Cummins
Jack Cummins
17,417 Points
Jack Cummins
Jack Cummins
17,417 Points

Steve Hunter Thank You for Helping Me! By the way, who's that person on your profile picture??

Steve Hunter
Steve Hunter
57,712 Points

The person on my profile picture, amazingly, is me! :smile:

Steve Hunter
Steve Hunter
57,712 Points

It's a triathlon called an Ironman. The photo is of me crossing the finish line in Kalmar, Sweden in August 2014. An Ironman is a long distance triathlon consisting of a 2.4 mile sea swim, a 112 mile bike ride and then a 26.2 mile run, all done consecutively with no breaks. Tough day out - 140.6 miles across the three disciplines. I highly recommend trying one; such a great feeling when you finish!

Steve Hunter
Steve Hunter
57,712 Points

Hi! :+1:

Steve Hunter
Steve Hunter
57,712 Points

We've got Twitter or Facebook for this! :wink:

ianuweocrs
ianuweocrs
6,958 Points
ianuweocrs
ianuweocrs
6,958 Points

Hi ! In the normalizeDiscountCode, you have to check whether it countains something else than a letter or '$'. You can simply do it by iterating over all the characters of the String given in parameter, like this :

for (char c: discountCode.toCharArray())
      if ( !((c >= 'A' && c <= 'Z') || c == '$') )
             throw new IllegalArgumentException("Invalid discount code");

I let you implement the rest of the code