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Java Java Objects (Retired) Delivering the MVP Validation

Mihai Andrei
Mihai Andrei
612 Points
Posted by Mihai Andrei
Mihai Andrei
612 Points

Throwing an exception

I have to throw an exception if the string fieldName is not validating the 2 conditions:

public static String validatedFieldName(String fieldName) { if ( fieldName.indexOf(0)!=('m'))
{throw new IllegalArgumentException ("is not starting with an 'm'");} if (!('A'<= fieldName.indexOf(1)) && (fieldName.indexOf(1) <= 'Z')) {throw new IllegalArgumentException (" not uppercase");}

// 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
return fieldName;

//Thanks for answering

TeacherAssistant.java 
public class TeacherAssistant {

 public static String validatedFieldName(String fieldName) {
    if ( fieldName.indexOf(0)!=('m'))  
  {throw new IllegalArgumentException ("Nu e ok");}
    if (!('A'<= fieldName.indexOf(1)) && (fieldName.indexOf(1) <= 'Z')) 
      {throw new IllegalArgumentException ("Nu e okey");}

    // 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;
  }

}

3 Answers

Allan Clark
Allan Clark
10,810 Points
Allan Clark
Allan Clark
10,810 Points

Your first if statement checks if the index of the int 0 is 'm'. The indexOf() method always returns an int so it will never be == to 'm' so it always throws the exception. You pass the indexOf() method a String, the method checks the String it was called on and returns the index of what was passed to it.

String str = "Hello World";

str.indexOf("H");
// returns 0

str.indexOf("z");
// returns -1

str.indexOf(492);
// returns -1
Mihai Andrei
Mihai Andrei
612 Points
Mihai Andrei
Mihai Andrei
612 Points

Thanks a lot, Allan!

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"