How do I get Character.isLetter() to work?

Question

Hey guys! I don't understand why my Character.isLetter() method isn't working. The computer was telling me that the original problem was that it could only check char's and my input was a String, so I changed the return value and the String declaration both to char's. Despite that, it's still not working. Any ideas?

In case it helps, this is the exact language of the question. 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 char discountCode;


  private char normalizeDiscountCode(char discountCode){
    if (! Character.isLetter(discountCode)) {
    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(char 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"
    }

  }
}

Answer 1 · 2017-05-20T22:45:27Z

May 20, 2017 10:45pm

Your discount code needs to be a string not a char. When it tries to apply a discount code it will pass in a whole string, and when it tries to get the discount code it expects a whole string in return. But when you validate that the discount code is the right characters, you'll need to do it character by character, so I used a loop:

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);
  }
}

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Kaytlynn Ransom

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How do I get Character.isLetter() to work?

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