normalizeDiscountCode => NullPointerException - why?

Question

What is wrong here?

private String normalizeDiscountCode(String aDiscountCode) { String newString = aDiscountCode.toUpperCase(); return newString; }

I am returning the upper case version of the String aDiscountCode. Why is there an error here?

Isn't this what I am asked to do? Transform a string to upper case?

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;
  }

  private String normalizeDiscountCode(String aDiscountCode) {
    String newString = aDiscountCode.toUpperCase();
    return newString; 
  }

  public String getItemName() {
    return itemName;
  }

  public int getPriceInCents() {
    return priceInCents;
  }

  public String getDiscountCode() {
    return discountCode;
  }

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

Answer 1 · 2017-07-07T15:31:42Z

July 7, 2017 3:31pm

Hi Massimo,

The issue here seems to be the call to normalizeDiscountCode. The compiler is complaining about the parameter you are sending out of applyDiscountCode. It doesn't like the fact that the class member variable is being passed, this.discountCode. If you just pass discountCode it work fine; in terms of the exception, anyway. I'm not sure but this may be because this.discountCode is private; perhaps that means it can't be directly passed - without loading the code into Intelli-J to get more detailed error messages, I can't tell.

Back to the challenge, though. In normalizeDiscountCode for the first part of this challenge, you just want to return the received string in upper case form. We don't need to create a new string variable, but you can if you want to. Fewer lines of code would look like:

  private String normalizeDiscountCode(String aDiscountCode) {
    return aDiscountCode.toUpperCase();
  }

Inside applyDiscountCode, assign the returned value from normalizeDiscountCode into this.discountCode. The parameter you send to normalizeDiscountCode is the same that this method receives. Don't send the member variable directly.

  public void applyDiscountCode(String discountCode) {  // <- send that one
    this.discountCode = normalizeDiscountCode(discountCode); // <- no 'this' here
  }

I hope that makes sense.

Steve.

Answer 2 · 2017-07-07T15:45:04Z

July 7, 2017 3:45pm

There was a problem with the compiler as even something like this didn't work:

public String normalizeString(String aString) 
{
   return aString.toUpperCase();
}

Which works in other IDEs. After I restarted everything worked again properly.

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Massimo Scola

Massimo Scola

normalizeDiscountCode => NullPointerException - why?

2 Answers

Steve Hunter

Steve Hunter

Massimo Scola

Massimo Scola

Steve Hunter

Steve Hunter