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Start your free trialJohn Grillo
30,241 PointsJava 'getFirstName' is written but quiz pretends it doesn't exist. What do?
I am currently trying to finish this Java quiz but for this part, the exercize seems to ignore the fact that I do have a 'getFirstName' method written. I have no idea what is going on and why it isn't working. Any insight would be appreciated.
public class Forum {
private String topic;
// TODO: add a constructor that accepts a topic and sets the private field topic
public forum(String topic) {
this.topic = topic;
}
public String getTopic() {
return topic;
}
/* Uncomment this when you are prompted to do so
public void addPost(ForumPost post) {
System.out.printf("A new post in %s topic from %s %s about %s is available",
topic,
post.getAuthor().getFirstName(),
post.getAuthor().getLastName(),
post.getTitle()
);
}
*/
}
public class User {
// TODO: add private fields for firstName and lastName
private String firstName;
private String lastName;
public User(String firstName, String lastName) {
// TODO: set and add the private fields
firstName = this.firstname;
lastname = this.lastName;
}
// TODO: add getters for firstName and lastName
public String getFirstName() {
return firstname;
}
public String getLastName() {
return lastName;
}
}
public class ForumPost {
private User author;
private String title;
private String description;
// TODO: add a constructor that accepts the author, title and description
public User getAuthor() {
return author;
}
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
}
public class Main {
public static void main(String[] args) {
System.out.println("Beginning forum example");
if (args.length < 2) {
System.out.println("Usage: java Main <first name> <last name>");
System.err.println("<first name> and <last name> are required");
System.exit(1);
}
/* Uncomment this when prompted
Forum forum = new Forum("Java");
// TODO: pass in the first name and last name that are in the args parameter
User author = new User();
// TODO: initialize the forum post with the user created above and a title and description of your choice
ForumPost post = new ForumPost();
forum.addPost(post);
// */
}
}
2 Answers
Steve Hunter
57,712 PointsHi John,
A few things here:
- Constructors are named after their class and are capitalised; your
forum
constructor has a lowercase f. - Your
User
constructor is settingfirstName = this.firstName
- that needs to be the other way round;this.firstName = firstName;
- In your
getFirstName
method you are returningfirstname
notfirstName
- capitalise the 'N'
I hope that helps,
Steve.
Steve Hunter
57,712 PointsYou're setting the value of the member variable of the class, firstName
to be equal to the value passed in as the argument, firstName
. To distinguish the two, and a good IDE will do that for you, the member variable is identified with this
to indicate that the variable you are setting is part of the instance you are working within. So, this.firstName
is the member variable of the instance of the class you are working with; firstName
is the received argument passed into the constructor. You set the former to equal the latter. The former holds no value yet; that's what the constructor is there to do; construct the instance.
Make sense?
Steve.
John Grillo
30,241 Pointsoh, so this
in this particular case refers to an instance of the class, not the narrower scope of the that method?
Maybe I should watch that video again...if I could find it.
Steve Hunter
57,712 PointsYes. The keyword this
is used with a class to indicate that the action is to take place on a member of this
instance. If you get instances, you'll come to get this
. Indeed, just carrying on and not dwelling on the detail is probably the best thing to do. It really does all become familiar in no time. Other languages; Swift and Python to name two that I know of; use self
rather than this
- it indicates ownership, uniqueness and entity better, in my view. Same gig, though. When dealing with class definitions, remember these are never used alone; they create instance/objects which are unique - the class itself is just a template - it never exists on its own. (There are exceptions to that - but let's worry about that later!!)
John Grillo
30,241 PointsJohn Grillo
30,241 PointsIt does, thank you. why does this.firstName have to be on the right, like
this.firstName = firstName;
?