Hands-On Design Patterns with Java

Programming the design pattern

The StudentDashboard class extends the Observable class and has a single class variable, the unreadMessages int. There are three methods in this class: the constructor class and the setter (mutator) and getter (accessor) methods:

public class StudentDashboard extends Observable {    private int unreadMessages;    // constructor    public StudentDashboard() {        unreadMessages = 0;    }    public void setUnreadMessages(int messages) {        unreadMessages = messages;        /*            Add methods here to notify observers of a change         */    }    public int getUnreadMessages() {        return unreadMessages;    }}

The ForumMonitor class implements the Observer interface. It includes a final UNREAD_ALERT_LEVEL variable that is used as an alert threshold. In our example, ...