Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Java Java Objects (Retired) Delivering the MVP Validation

Daniel Schwemmlein
Daniel Schwemmlein
4,960 Points
Posted by Daniel Schwemmlein
Daniel Schwemmlein
4,960 Points

How do i check if a letter starts with m and that the second letter is uppercased?

Hey guys! So in this challenge I'm supposed to check if the fieldname starts with an m and then goes on with camelcased letters, so the m lowercased and everything else uppercased. If not I should throw an illegalargumentexception. I kind of know how to do the latter. but the first part I have no idea. Its probably something with char. Please help me. Thanks!

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
    if (! isvalidatedFieldName) {
      throw (illegalArgumentException iae) {
        console.printf("Please try again");
      }
    }
    return fieldName;
  }

}

3 Answers

Ken Alger
STAFF
Ken Alger
Treehouse Teacher
Ken Alger
Ken Alger
Treehouse Teacher

Daniel;

You can check the status of characters in fieldName with the zero-based index method of charAt(). For example we want to make sure that "fieldName.charAt(0) == 'm'", or more specifically "fieldName.charAt(0) != 'm'".

A couple of things with this challenge to consider with your code, when checking the second character you also need to check that it is a letter.

Hopefully that gets you pointed in the right direction.

Happy coding,

Ken

Daniel Schwemmlein
Daniel Schwemmlein
4,960 Points
Daniel Schwemmlein
Daniel Schwemmlein
4,960 Points

should it look like this then?
Sorry, this one is really difficult for me

if (! isvalidatedFieldName) { fieldName.charAt(0) != 'm'; throw (illegalArgumentException iae) { console.printf("Please try again");

Ken Alger
STAFF
Ken Alger
Treehouse Teacher
Ken Alger
Ken Alger
Treehouse Teacher

Daniel;

Inside the validatedFieldName function, you can do something like:

    if(fieldName.charAt(0) != 'm' ){
      throw new IllegalArgumentException("Error, needs to start with letter 'm'.");
    }

Then you will need to check the requirements for charAt(1) to make sure that character passes as well.

Ken