Expand SimpleXmlScanner to add tokens for XML comments, DOCTYPE declarations, CDATA sections, and both element and attribute declarations in the DTD (to support validating parsers).

Make the AbmlParser implement the ErrorHandler interface and appropriately handle the three levels of errors reported by a SAX-compliant parser.

Improve the BookmarkViewer application by adding two buttons (and their associated behaviors): Sort and Add. Sort will sort the bookmark names in the list. Add will allow you to add an additional bookmark to the list (note: this will require an additional text field for the URL name).

Using AElfred and the javax.swing classes, develop an applet that will display an XML document using a JTree.