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Java Java Objects (Retired) Delivering the MVP Validation

Posted by Carter Pringle
Carter Pringle
3,416 Points

Stage 4 exercise question

This should work, yet it doesn't. I mean it checks if the name is correct, and if so it returns it, otherwise it returns failed. There's no code errors, but it says "Expected firstName to fail, but it passed." Or something along those lines. This question is seriously getting on my nerves!

TeacherAssistant.java 
public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    try {
            if (fieldName.startsWith("m")) {
                if (Character.isUpperCase(fieldName.charAt(1))) {
                    return fieldName;
                }
            }
        } catch (IllegalArgumentException iae) {

        }
        return "failed";
  }

}

2 Answers

Jon Kussmann
PLUS
Jon Kussmann
Courses Plus Student 7,254 Points
Jon Kussmann
Jon Kussmann
Courses Plus Student 7,254 Points

It's a little tricky, but the question is asking you to throw an exception, not try to catch it.

Modifying your code a little...

if (fieldName.startsWith("m") && Character.isUpperCase(fieldName.charAt(1))) {
      return fieldName;
    } else {
      throw new IllegalArgumentException("Invalid name");
    }
Carter Pringle
Carter Pringle
3,416 Points

Awesome, thanks a bunch!

Youngchul Kim
Youngchul Kim
4,258 Points

Jon, could you briefly explain why I must use Character.isUpperCase in this scenario? Why do I get an error when using fieldName.isUpperCase?

Jon Kussmann
Jon Kussmann
Courses Plus Student 7,254 Points
Jon Kussmann
Jon Kussmann
Courses Plus Student 7,254 Points

Sure,

The isUpperCase method is a static method. This means that it is called by the class, and not any one specific object of that class.

fieldName is a string and it does not have a method that you can give an index to see if it is upper case or not (it's just not built into Java.

The Character class does have such method, all you need to do is give it a char and it will tell you if it's uppercase or not.

(You give it a char, by getting the character from the 1 position of the string)

Let me know if anything needs more explanation.

Jess Sanders
Jess Sanders
12,086 Points
Jess Sanders
Jess Sanders
12,086 Points 
private char validateGuess(char letter) {
    if (!Character.isLetter(letter)) {
      throw new IllegalArgumentException("A letter is required."
    }
    letter = Character.toLowerCase(letter);
    if (mMisses.indexOf(letter) >= 0 || mHits.indexOf(letter) >= 0) { 
      throw new IllegalArgumentException(letter + " has already been guessed")           }
    return letter;
  }
  • The above code is the example to follow.
  • We care about charAt for this challenge, rather than indexOf
  • In pseudocode, we want to check for the following condition, and throw an error: " if the character at index 0 of fieldName does not equal 'm' OR the character at index 1 of fieldName is not upper case"