Programming Internet Email

Creating JBiff

JBiff will not take much code, so we can define it in a single class in a single file. As we will see, that is a fib; we will need another small class to handle a mouse event on the window’s “kill” button, but more on that later. It is generally good OO style to separate the GUI from the logic, but we won’t get too hung up on that. Now, to structure the class: as with any Java class, we will have to create a constructor. The constructor creates an instance of the JBiff class and shows the basic GUI. The class’s main () method is where the action takes places; it will connect to an IMAP server, retrieve the information, and then cause it to be displayed in the GUI.

The first thing that we need to do is import references to the various Java packages that we will be using—some from JAF and the Java Mail API and others from the more mundane java.awt and java.util packages in the core. Those classes in the javax. mail package are in Java Mail API. Those in the javax.activation package are part of the JAF.

import javax.mail.*;
import javax.mail.event.*;
import javax.mail.internet.*;
import javax.activation.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;

Our class represents the JBiff GUI; all of the logic is in the main () method. To make things easy, we will have our GUI class extend Frame, which will create a frame when the class is instantiated. We will also need a label on which to write our mailbox status message. The class starts this way:

public class ...