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Java Java Objects (Retired) Delivering the MVP Wrapping up

ForumPost

In one of the challenges, the code is as follows:

public class ForumPost { private User mAuthor; private String mTitle; private String mDescription;

}

I understand String as a primitive type, but I don't know what is User as a type? What is it, and in what way is it used?

ForumPost.java
public class ForumPost {
  private User mAuthor;
  private String mTitle;
  private String mDescription;

  public ForumPost(User author, String title, String description) {
      mAuthor = author;
      mTitle = title;
      mDescription = description;      
  }

  public User getAuthor() {
    return mAuthor;
  }

  public String getTitle() {
    return mTitle;
  }

  public String getDescription() {
    return mDescription;
  }

  // TODO: We need to expose the description
}
User.java
public class User {
    private String mFirstName;
    private String mLastName;

  public User(String firstName, String lastName) {
    // TODO:  Set the private fields here
      mFirstName = firstName;
      mLastName = lastName;
  }

  public String getFirstName() {
    return mFirstName;
  }

  public String getLastName() {
    return mLastName;
  }


}
Forum.java
public class Forum {
  private String mTopic;

  public Forum(String topic)  {
      mTopic = topic; 
  }

  public String getTopic() {
      return mTopic;
  }

  public void addPost(ForumPost post) {
      // When all is ready uncomment this...
      System.out.printf("New post from %s %s about %s.\n",
                         post.getAuthor().getFirstName(),
                         post.getAuthor().getLastName(),
                         post.getTitle());
  }
}
Example.java
public class Example {

  public static void main(String[] args) {
    System.out.println("Starting forum example...");
    if (args.length < 2) {
       System.out.println("first and last name are required. eg:  java Example Craig Dennis");
    }
       Forum forum = new Forum("Java");
    // Take the first two elements passed args
       User author = new User("Steven", "Williams");
    // Add the author, title and description
       ForumPost post = new ForumPost("Java", "Learn it");
    // forum.addPost(post);
  }
}

1 Answer

String isn't a primitive type, it is a class. Java wrote a "String" class for everyone so that you don't have to write your own String class. The "User" type is defined in the User class located in User.java that Treehouse wrote for you so that you didn't have to write it.

The usage of primitive types vs. classes to define a variable are the same, except that classes start with an upper case letter (i.e. int vs. Integer, double vs. Double).

Thank you for the reply. And thanks for the String is a class correction. For the "User" type, what is allowed to be assigned to it? In other words, if int allows for numeric values such as 1, 2, 100 etc., and boolean returns true or false, how or in what way is "User" actually used? Thanks!