THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
...
The reference for concurrency in Java, here is note from 2015 by the author about the pertinence of this 10+ years old book.
To learn more about Refactoring, the natural starting point is the Refactoring Book. You should also have a look at the online catalog of refactorings
...
Groovy and Gradle
"Groovy in action (2nd edition)"
...
This book covers general information about the XSL-FO standard from W3C and has extensive example of how to achieve specific effects and such.