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Java Java Objects Delivering the MVP Applying a Discount Code

Posted by Nikolai Pütz
Nikolai Pütz
965 Points

i have no idea :(

I searched on the internet and everything i understand that if you have a character you can just do character.isLetter but with a string i dont know how to do it. I saw some people did it with [a-z] stuff. I hope somebody can explain me how to do it.

Order.java 
public class Order {
  private String itemName;
  private int priceInCents;
  private String discountCode;

private String normalizeDiscountCode ( String discountCode){
  String normalizeDiscountCode = discountCode.toUpperCase();

  return normalizeDiscountCode;



}



  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) {
    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"
    }

  }
}

1 Answer

Alexander La Bianca
Alexander La Bianca
15,959 Points

Hi Nikolai,

What you can do is to loop through the length of the discountCode using a while loop. Here is what this code could look like

private String normalizeDiscountCode(String discountCode) throws IllegalArgumentException{
    int i = 0; //initialize counter to start at the beginning of the discountCode
    while(i < discountCode.lenght()) {   //while loop through the discountCode to validate each character
        char nextLetter = discountCode.charAt(i);
        if(Character.isLetter(nextLetter) || nextLetter == '$') {
            i++ ;     //if it is either a letter or $ then increase the counter to get the next letter. 
        }
        else {
           IllegalArgumentException exc = new IllegalArgumentException("Invalid discount code");  //throw the exception
           throw exc;
        }
    }
    return discountCode.toUpperCase(); //this is only reached if the exception is never thrown meaning a valid discountCode
  }

You can think of a string like an array that you can loop through and then treat each index like a char. You were close by knowing about the Character.isLetter() method.