I can't give a definitive answer, but you might start by looking to see if the
ZipFile class (and associated stream classes) can do what you require. A jar is
just a Zip file.

..

Abso(frigging)lutley! If you have some code that is *failing*
to find XML (GIF, txt, whatever) files within the jar's on the
*classpath* of the application, give us an SSCCE and we
can provide futrher pointers* as to getting access to (non
class) resources within jar archives.

* There are some quirks to loading resources that regularly
catch people up, but the possibilities are too many to pin
down, without code. An SSCCE** that fails for you, might
help there.

** <http://www.physci.org/codes/sscce.html>

As an aside.  An URL for any 'failing' applet can really
help debugging.  Is you applet 'live'?  What is the URL?

Bryan schrieb:

Because you have also packages and class files in your jar file, I
assume the jar file is part of your classpath.
Then you can use the classloader to get your XML file:
  URL url = getClass().getResource("/my/foo/package/bar.xml");
  System.out.println("url = " + url);
  if (url == null)
    throw ...;
  parser.parse(url.toString());

To understand why this should work, there are some API docs to be read:
Class#getResource, URL, Parser#parse

Here are two methods:
1. Use ZipEntry and ZipInputStream, see
http://mindprod.com/jgloss/zip.html
2. use a xxx:jar URL, see  http://mindprod.com/jgloss/uri.html