how to upload with java applet?

Is it possible to upload files with java applet via http post? Is it very hard to do? I can't find any tutorials about it, only loads of upload applets.

Yes, it's possible. Try an upload applet such as JFileUpload. It supports both HTTP and FTP upload:
http://www.jfileupload.com/products/jfileupload/index.html

It relies on HTTP protocol implementation with POST support.

I hope it helps.