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Start your free trialArne Stops
642 PointsWhat is wrong here? I don´t understand the Compiler error...(Nullpointer)
I just don´t understand this...
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 discountCode) {
discountCode = this.discountCode.toUpperCase();
return discountCode;
}
public String getItemName() {
return itemName;
}
public int getPriceInCents() {
return priceInCents;
}
public String getDiscountCode() {
return discountCode;
}
public void applyDiscountCode(String discountCode) {
this.discountCode = normalizeDiscountCode(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"
}
}
}
1 Answer
Florian Tönjes
Full Stack JavaScript Techdegree Graduate 50,856 PointsHi Arne,
this.discountCode refers to the discountCode private field of the Order class. You are trying to call the toUpperCase() method on this field, which has not been initialized.
This is how you can fix it:
private String normalizeDiscountCode(String discountCode) {
this.discountCode = discountCode.toUpperCase();
return this.discountCode;
}
Now this.discountCode is on the left side and the value of "discountCode.toUpperCase()" gets assigned to it. "This" always refers to the field of the class, not to the parameter of the method.
Kind Regards, Florian