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Java Java Objects (Retired) Delivering the MVP Validation

Posted by ahmed alghafli
ahmed alghafli
3,446 Points

So I was wondering if you could help me with some of these code challenges. As you might've see

I'm confused with this question ???

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) {
    if (! fieldName.isUppercase(fieldName)) {
     throw new IllegalArgumentException("uppercase letter is required");
    }


    // 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;
  }

}

5 Answers

William Li
PLUS
William Li
Courses Plus Student 26,868 Points
William Li
William Li
Courses Plus Student 26,868 Points

hi, ahmed, there're couple things the if condition needs to check here.

  1. Member fields must start with an 'm'
  2. The second letter in the field name must be uppercased to ensure camel-casing

So only doing !fieldName.isUppercase(fieldName) is not enough here.

public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    if (fieldName.charAt(0) != 'm' || !Character.isUpperCase(fieldName.charAt(1)) ) {
        throw new IllegalArgumentException(" Illegal field name "); 
      }
    return fieldName;
  }
}

Note, I never take this Java course here at Treehouse, so I am not sure how the instructor'd want you to approach this problem, but Character.isUpperCase(fieldName.charAt(1)) is the way I know of to check for the 2nd condition.

ahmed alghafli
ahmed alghafli
3,446 Points

it doesn't work ?!!! but thanks foe helping !!

ahmed alghafli
ahmed alghafli
3,446 Points

it always telling me that : can't find symbol

Gabi Beyer
Gabi Beyer
2,139 Points
Gabi Beyer
Gabi Beyer
2,139 Points

I remember getting stuck on this one too! You also have to check if it is a letter, so that they do not use a symbol in the fieldName.

public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    if (fieldName.charAt(0) != 'm' || 
    !Character.isLetter(fieldName.charAt(1)) ||
    !Character.isUpperCase(fieldName.charAt(1)) ) {
        throw new IllegalArgumentException(" Illegal field name "); 
      }
   return fieldName;
  }

}
ahmed alghafli
ahmed alghafli
3,446 Points

still the same ,,

Gabi Beyer
Gabi Beyer
2,139 Points

Post your code

Gabi Beyer
Gabi Beyer
2,139 Points
Gabi Beyer
Gabi Beyer
2,139 Points

make sure when you check isLetter you are doing it for fieldName.charAt(1), (as compared to .charAt(0) or something) It is checking whether the second letter in the string is a letter and not a symbol

ahmed alghafli
ahmed alghafli
3,446 Points
ahmed alghafli
ahmed alghafli
3,446 Points

ohh thanks I pass the question but I don't know why !!!

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.

  • 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"

public class TeacherAssistant {

  public static String validatedFieldName(String fieldName) {
    if (fieldName.charAt(0) != 'm' || !Character.isUpperCase(fieldName.charAt(1))) {
      throw new IllegalArgumentException("The field name does not match the style");
    }
    return fieldName;
  }

}