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Start your free trialAnkit Nandi
750 PointsnullPointerException error
The Question
For this first task, create a new private method named normalizeDiscountCode. It should take the discount code that is passed into the method and return the uppercase version. Call it from the current applyDiscountCode method and set this.discountCode to the result.
The Error
java.lang.NullPointerException (Look around Order.java line 7)
public class Order {
private String itemName;
private int priceInCents;
private String discountCode;
private String normalizeDiscountCode(String str){
return str.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) {
normalizeDiscountCode(this.discountCode) ;
this.discountCode = discountCode;
}
}
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
andren
28,558 PointsOn the first line of your applyDiscountCode
method you pass the contents of this.discountCode
into the normalizeDiscountCode
method. But at that point nothing has been assigned to this.discountCode
, so you pass null as a value.
Therefore when toUpperCase()
is called on it in the normalizeDiscountCode
method, a null-pointer exception is raised.
What you should be passing into the method is actually discountCode
the parameter, also you should combine your two lines into one like this:
public void applyDiscountCode(String discountCode) {
this.discountCode = normalizeDiscountCode(discountCode);
}
That way this.discountCode
will be assigned to whatever the normalizeDiscountCode
returns. Which is what the instructions of the task asked you to do.
Steve Hunter
57,712 PointsHi Ankit,
Your normalize method is fine. However, if the applyDiscountCode
method, you want to pass the parameter into normalize and assign the returned value into this.discountCode
. So, applyDiscountCode
receives the code as an incoming string. - pass that into the normalize method, assign the result that it returns into the member variable.
That looks like:
private String normalizeDiscountCode(String str){
return str.toUpperCase() ;
}
public void applyDiscountCode(String discountCode) {
this.discountCode = normalizeDiscountCode(discountCode);
}
Steve.