Based on the information you provided I feel that my son should prepare for "OCP Java 11 Developer certification"/Exam # 1Z0-819
But where are the books to prepare for this?
This seems to be not right for this:
Though they are claiming:
NOTE: After the release of the Developer Complete Study Guide, Oracle completely revamped the Java SE 11 certification by retiring Exams 1Z0-815 and 1Z0-816. You're now only required to pass the new Exam 1Z0-819. The Upgrade Exam 1Z0-817 remains the same. Even though the exams have changed, the same topics are covered (but are presented in a different order). You can rest assured, however, that this Certification Kit provides complete coverage of the Java SE 11 certification exam.
There is a practice tests:
Then I went thru this link: