Improving structure with inheritance - Objects First with Java: A Practical Introduction Using BlueJ - page 280

Code 8.3
Source code of the
NewsFeed class

import java.util.ArrayList;

/**
* The NewsFeed class stores news posts for the news feed in a
* social-network application (like FaceBook or Google+).
*
* Display of the posts is currently simulated by printing the
* details to the terminal. (Later, this should display in a browser.)
*
* This version does not save the data to disk, and it does not
* provide any search or ordering functions.
*
* @author Michael Kölling and David J. Barnes
* @version 0.1
*/
public class NewsFeed
{

private ArrayList<MessagePost> messages;
private ArrayList<PhotoPost> photos;

/**
* Construct an empty news feed.
*/
public NewsFeed()
{

messages = new ArrayList<MessagePost>();
photos = new ArrayList<PhotoPost>();

}

/**
* Add a text post to the news feed.
*
* @param text The text post to be added.
*/
public void addMessagePost(MessagePost message)
{

messages.add(message);

}

/**
* Add a photo post to the news feed.
*
* @param photo The photo post to be added.
*/
public void addPhotoPost(PhotoPost photo)
{

photos.add(photo);

}