Where can a student independently learn elementary recursion, preferably in Java?
Often times, google is our best of friends (I hope). A rather simple search leads to a very informative site: 

http://introcs.cs.princeton.edu/java/23recursion/

It is very thorough, and explains many use-cases for recursion. 

Another very handy resource is, inevitably, Stack Overflow: this question also provides some information, but it is rather specific. Instead of staying there, one can navigate to the Related Questions section, and from there choose a promising question (usually the one with the highest votes, but not always) and reading it. And so on, and so on... (recursively ;)).