SlideShare is the best way to share your presentations with the world.
Let your ideas reach a broad audience. Share publicly or privately.
Add audio to create a webinar.

A search for Joomla return 125 presentations! while Spring java return 4897 presentations!

You can download them free of charge, but that require a free registration.
Not all of them are top quality, but who knows with such number of files,
some may help you.