Java and Electronic Mail - Java - page 707

more than one folder containing messages. For this we'll use a JTree widget, the Swing GUI
component for displaying text or icons in a tree-like view. The objects stored in a JTree must
be Node objects, but we also want them to be Folders and Messages . I handled this by sub-
classing DefaultMutableNode and adding a field for the folder or message, although you
could also subclass Folder and implement the Node interface. Arguably, the way I did it is
less “pure OO,” but also less work. Example 17-8 is my MessageNode ; FolderNode is simil-
ar, but simpler in that its toString() method calls only the Folder 's getName() method.

Example 17-8. MessageNode.java
public public class class MessageNode MessageNode extends extends DefaultMutableTreeNode {

Message m ;

StringFormat fromFmt = new new StringFormat ( 20 , StringFormat . JUST_LEFT );

StringFormat subjFmt = new new StringFormat ( 30 , StringFormat . JUST_LEFT );

MessageNode ( Message m ) {
this this . m = m ;

}

public public String toString () {

try try {

Address from = m . getFrom ()[ 0 ];

String fromAddress ;
iif ( from instanceof instanceof InternetAddress )

fromAddress = (( InternetAddress ) from ). getAddress ();

else

fromAddress = from . toString ();

StringBuffer sb = new new StringBuffer ();

fromFmt . format ( fromAddress , sb , null

null );

sb . append ( " " );
subjFmt . format ( m . getSubject (), sb , null

null );

return sb . toString ();
} catch

return

catch ( Exception e ) {
return

return e . toString ();

}

}

}

These are all put together into a mail reader component in Program: MailReaderBean .