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Java Java Objects Delivering the MVP Applying a Discount Code

Daniel Hunter
Daniel Hunter
4,622 Points
Posted by Daniel Hunter
Daniel Hunter
4,622 Points

can someone give me some pointers on normalisation on strings?

I am struggling to work out how to only allow letters or specific symbols to be passed in by the user. i tried converting the sting to a char array to call the Character.isLetter method on the char array but can't get it to work (see the commented code I moved to the bottom). please help.

Dan

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){
    if (! Character.isLetter(discountCode)){
    throw new IllegalArgumentException("Invalid discount code."); 
   }    
    discountCode = discountCode.toUpperCase();
    return discountCode;

  }

}

/*for (char discountCodeCharacters = discountCode.toCharArray()){
       if (! Character.isLetter(discountCodeCharacters)|| == '$'){
     throw new IllegalArgumentException("Invalid discount code."); 
      } 
    }*/   // 1st attempt
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

Yanuar Prakoso
Yanuar Prakoso
15,196 Points
Yanuar Prakoso
Yanuar Prakoso
15,196 Points

Hi Daniel

First of all you need to examine each character in the discountCode thus since discountCode is a String you need to convert it first to an array of characters. After that you can use for loops to iterate each character in the array of characters and validate its content.

Now for the IF statement. The validation said that IF the characters is NOT (a letter OR '$') the THROW something right? Therefor the IF statement should sound like this:

**IF (NOT(character is a Letter || charcater is 'S')) --> PS: character in Java uses single quotes (' ') while Strings uses double quotes (" ") and || means OR.

please note another thing Character.isLetter(character to be tested) is a method for Character (char) type object not String type object. Therefor you cannot just insert discountCode to the method like you did in your code. You need to test it using the character from the array list created from discountCode.

Here is my code if you want some reference:

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

  private String normalizeDiscountCode(String discountCode){

    char[] letters = discountCode.toCharArray(); //<--change it to array of characters first

    for (char letter : letters){//<--for loop each character in the array of characters

      if (! (Character.isLetter(letter) || letter == '$')){//<--the correct IF statement
      throw new IllegalArgumentException("Invalid discount code."); 
      }
    }
    discountCode = discountCode.toUpperCase();
    return discountCode;
  }

I hope you can understand by reading the code. I hope this can help.

Daniel Hunter
Daniel Hunter
4,622 Points
Daniel Hunter
Daniel Hunter
4,622 Points

Hi Yanuar,

Thanks that helped a lot, I knew I was getting close with my first attempt but I just couldn't get it to work. thank you.