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Start your free trialChris Gauthier
Courses Plus Student 6,434 PointsChecking a string has only letters.
Hello,
Im looking to check a string to see if it contains only letters. I can use a char.isLetter() to do this with a char, but Im looking for something like this for a String. A quick search on the java API site didn't get me anything that looked fruitful. Can you guys steer me in the right direction?
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) {
if (discountCode.isLetter() || discountCode == "$") {
return discountCode.toUpperCase();
}
else {
throw new IllegalArgumentException("Only letters and $ sign's are allowed");
}
}
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
Craig Dennis
Treehouse TeacherHi Chris!
Your code works and was more or less what I was intending at this point in time. You'll want to loop toCharArray
on the discount code and do that check.
You could do this with a regular expression and use the match
method. Again extra credit here but I did a workshop on regular expressions in Java that you might want to check out.