I am a lecturer since 2002 and I have taught Java at Masters level (level 9) since 2013. Specifically, I have taught Java Fundamentals in addition to both the Oracle Java Certification Associate (OCA) and Professional (OCP) certification syllabii. This is on behalf of a highly regarded software company. On completion of my training, graduates then face the company's own internal Java Certification exam (similar in style to Oracle's). I have no visibility into the questions they will face. It is a 3 hour long intensive exam. This means that my work is externally validated. The company are delighted with the pass rate (100% since year 1).
I love teaching and believe diagrams/code help greatly. I have a strong attention to detail which lends itself perfectly to the Oracle Java Certification exams. I am delighted that Enthuware (the excellent Java Certification training tool), have, in their explanations, linked to my YouTube channel.