Improving structure with inheritance - Objects First with Java: A Practical Introduction Using BlueJ - page 287

defined in class Post , and the other a value for a field defined in class MessagePost . All of
these fields must be correctly initialized, and Code 8.4 shows the code segments that are used
to achieve this in Java.

Code 8.4
Initialization of subclass
and superclass fields

public class Post
{

private String username; // username of the post's author
private long timestamp;
private int likes;
private ArrayList<String> comments;

/**
* Constructor for objects of class Post.
*
* @param author The username of the author of this post.
*/
public Post(String author)
{

username = author;
timestamp = System.currentTimeMillis();
likes = 0;
comments = new ArrayList<String>();

}

// Methods omitted.

}

public class MessagePost extends Post
{

private String message; // an arbitrarily long, multi-line message

/**
* Constructor for objects of class MessagePost.
*
* @param author The username of the author of this post.
* @param text The text of this post.
*/
public MessagePost(String author, String text)
{

super (author);
message = text;

}

// Methods omitted.

}