* Update a Java book URL - #2990

Changes:
- The book 'Object-Oriented vs. Functional Programming' has a .csp link
- Also a sign-up is required to read the book since it's hosted at oreilly.com
- The contributing guide is against a hosting service and required sign-up.
- That is why this PR is created.

* remove ? link
Co-authored-by: NEric Hellman <eric@hellman.net>