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Java Java Objects (Retired) Delivering the MVP Validation

I don't get this challenge

So I was wondering if you could help me with some of these code challenges. As you might've seen when a member field name doesn't match the style we've talked about, I send an error about it. Let's write some code to validate the style of the field name.

I've added the method validatedFieldName it will return the validated field name. If the value passed in doesn't meet the requirements, throw an IllegalArgumentException. I'll keep you posted on the results every time you press check work.

TeacherAssistant.java
public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    // These things should be verified:
    // 1.  Member fields must start with an 'm'
    // 2.  The second letter in the field name must be uppercased to ensure camel-casing
    // NOTE:  To check if something is not equal use the != symbol. eg: 3 != 4
    return fieldName;
  }

}
Ethan Lowry
Ethan Lowry
Courses Plus Student 7,323 Points

What don't you get, specifically? What have you tried so far? The challenge wants you to take the 'fieldName' variable passed into this method, and then perform the actions described in the comments on it, before returning it.

9 Answers

Annamaria Toth
Annamaria Toth
6,617 Points

In you second if statement you have to define that the second character must be an upper case and must be a letter.

if ( Character.isLowerCase(secondChar) || Character.isLetter(secondChar)

It did pass for me.

You mean

if ( Character.isLowerCase(secondChar) || !Character.isLetter(secondChar)

You need to check if the fieldName string passed in to the function matches the requirements. If it does return fieldName unaltered, if it does not you need to throw an IllegalArgumentException.

How?

In first case you must check if the fieldName first character is equal to 'm' character if it's not then throw an exception like Craig did in previous lesson. In Second case first of all you must create a char variable to store second character of fieldName(remember counting begins from 0) for example secondChar then you should check if your new char variable secondChar(that is already stores second character of fieldName) has upperCase character..if it's not then throw an exception

I tried:

public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    char secondChar = fieldName.charAt(1);
     if (fieldName.charAt(0) != 'm' || secondChar.isLowerCase)
    {throw new IllegalArgumentException( fieldName + " is invalid.");}
    return fieldName;
  }

}

. . .But it said the char can't be dereferenced.

This is how you should do: Character.isLowerCase(secondChar)

You can read more about this features in java documentation as Craig in previous lessons.

Now it's saying "Bummer! Expected "m_first_name" to fail but it passed."

Did you passed this chalange?

No.

Jef Davis
Jef Davis
29,162 Points

I checked your code and ran into the same problem you're reporting when I tested it out. When I passed this challenge, I separated out the IllegalArgumentException into two separate if statements. I like the economy of your code, but I think trying to be so concise has lead you to the problem you're currently facing.

We have two objectives: throw an IllegalArgumentException if 1) The first character of the string does not equal 'm' and if 2) the second character of the string is not a letter OR is lower case

If you write these two objectives as separate if statements, you might have better results

http://docs.oracle.com/javase/7/docs/api/java/lang/Character.html

I tried:

public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    char secondChar = fieldName.charAt(1);
     if (fieldName.charAt(0) != 'm')
    {throw new IllegalArgumentException( fieldName + " is invalid.");}
    if (Character.isLowerCase(secondChar)) {throw new IllegalArgumentException( fieldName + " is invalid.");}
    return fieldName;
  }

}

But I am still getting the same thing ( Bummer! Expected "m_first_name" to fail but it passed. ).

Annamaria Toth
Annamaria Toth
6,617 Points

Yes, sorry that`s what I meant.

Thanks!!

It worked!!

The issue wasn't the fact that you needed to separate it into two if statements, the issue was the logic... and that you weren't checking to see if it was NOT a letter... the following code passes:

public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    char secondChar = fieldName.charAt(1);
    if (fieldName.charAt(0) != 'm' || Character.isLowerCase(secondChar) 
        || !Character.isLetter(secondChar)) {
      throw new IllegalArgumentException();
    }


    return fieldName;
  }

}