When I read some book for learning programming I almost always rewrite the code by myself. After that, I try to change something and see what will be happening. Sometimes I write some note from the book in the comment. So it is my working place where I try to learn java more deeply using a great book "Effective Java" by Joshua Bloch.
“Josh Bloch gives great insight into best practices that really can only be discovered after years of study and experience.” —Mark Mascolino, software engineer
Also sometimes I learn some design patterns and write it here too.