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Java Java Objects Creating the MVP Conference Registration Assistant

Posted by Juan Losauro
Juan Losauro
783 Points

Watched the video several times but can't understand this point

Really confusing to me

ConferenceRegistrationAssistant.java 
public class ConferenceRegistrationAssistant {

  /**
   * Assists in guiding people to the proper line based on their last name.
   *
   * @param lastName The person's last name
   * @return The line number based on the first letter of lastName
   */
  public int getLineNumberFor(String lastName) {
    int lineNumber = 0;
    /*
      lineNumber should be set based on the first character of the person's last name
      Line 1 - A thru M
      Line 2 - N thru Z

     */
    return lineNumber;
  }

}
Example.java 
public class Example {

  public static void main(String[] args) {
    /*
      IMPORTANT:  You can compare characters using <, >. <=, >= and == just like numbers
     */
    if ('C' < 'D') {
      System.out.println("C comes before D");
    }

    if ('B' > 'A') {
      System.out.println("B comes after A");
    }

    if ('E' >= 'E') {
      System.out.println("E is equal to or comes after E");
    }

    // This code is here for demonstration purposes only...
    ConferenceRegistrationAssistant assistant = new ConferenceRegistrationAssistant();
    /*
      Remember that there are 2 lines.
      Line #1 is for A-M
      Line #2 is for N-Z
     */
    int lineNumber = 0;
    /*
      This should set lineNumber to 2 because
      The last name is Zimmerman which starts with a Z.
      Therefore it is between N-Z
     */
    lineNumber = assistant.getLineNumberFor("Zimmerman");

    /*
      This method call should set lineNumber to 1, because 'A' from "Anderson" is between A-M.
     */
    lineNumber = assistant.getLineNumberFor("Anderson");

    /*
      Likewise Charlie Brown's 'B' is between 'A' and 'M', so lineNumber should be set to 1
     */
    lineNumber = assistant.getLineNumberFor("Brown");
  }

}
Craig Dennis
Craig Dennis
Treehouse Teacher
Craig Dennis
Craig Dennis
Treehouse Teacher

Hey Juan!

Can you clarify a little bit more about what is confusing to you, and I think people will be happy to help!

Thanks!

Juan Losauro
Juan Losauro
783 Points

What I don't understand is how can the first character of lastName be between A and M or N - Z.

What the challenge is asking me to do is to return a 1 if the first char of lastName is between A and M, or else return 2 if it is between N and Z. I can't figure out how to finish the challenge.

Mike Papamichail
Mike Papamichail
4,883 Points
Mike Papamichail
Mike Papamichail
4,883 Points

Juan Losauro , although i will post the solution below explaining how the method and the logic works, you should try even harder on your own :) i bet you can do it.Anyway, your method -after writting the code- should look something like this:

public int getLineNumberFor(String lastName) {
    int lineNumber = 0;
    if (lastName.charAt(0) >= 'A' && lastName.charAt(0) <= 'M') {
       lineNumber = 1;
    } else {
       lineNumber = 2;
    }
    /*
      lineNumber should be set based on the first character of the person's last name
      Line 1 - A thru M
      Line 2 - N thru Z

     */
    return lineNumber;
  }

Explanation: by calling the .charAt(0) method on a String, we are retrieving the first char-represented by the number 0- of that String-which is what the challenge wants us to do- and then we check if that first character of the lastName's string is greater than or equal to the char 'A'.The same goes for the other half inside the parentheses of the if statement.

Let's take for example, this line of code inside the Example.java file : 

lineNumber = assistant.getLineNumberFor("Zimmerman");

It calls the getLineNumberFor() method from the ConferenceRegistrationAssistant class-through the assistant object/instance- and passes in the String "Zinmmerman" as a parameter. Now like i explained above, in our method we get the first char of that String using the .charAt(0) method.So we are now comparing the char 'Z' with the char 'A' && with the char 'M'. If that condition is true(which is not) we return 1, if it's false(which is the case) we return 2-as intended-

Hope this helps!

Juan Losauro
Juan Losauro
783 Points

Ohh thank you sooo much bro! :))

Mike Papamichail
Mike Papamichail
4,883 Points
Mike Papamichail
Mike Papamichail
4,883 Points

Hey Juan Losauro , glad my answer helped you.Please make sure you mark it as a best answer so that other people with the similar problem can find the solution easier!