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Java Java Objects (Retired) Delivering the MVP Validation

should I use "if" statement and throw an exception outside the "if" statement? It never worked for me.

I tried solving this question, but never worked for me, should I use the throw outside or inside an "if" statement?

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;
  }

}

2 Answers

William Li
PLUS
William Li
Courses Plus Student 26,865 Points

should I use the throw outside or inside an "if" statement?

You definitely should throw exception inside the if condition check.

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

Check for these 2 conditions in your if statement, then throw exception.

If you're having trouble writing the if clause, here's one way to do it

if (fieldName.charAt(0) != 'm' || !Character.isUpperCase(fieldName.charAt(1)))

The rest should be easy.

This worked for me, I don't know how I couldn't think of using the "Character" object. Thanks for your help.

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"