For AI research, the most commonly used programming language is Lisp.
Lisp and Scheme have different syntax and many other differences.
Java is a very popular all-purpose programming language. It can be used in a lot of interesting stuff in AI / Functional Programming.
Many professionals also use C# and F#. Some people develop under Unix. Or Linux.
But the most popular and commonly used languages for AI nowadays are Python and R. These languages have a vast range of libraries and methods to explore different ways of automation using AI.
For upskilling yourself in Artificial Intelligence I would suggest you go with Intellipaat Artificial Intelligence Certification.
Hope this answer helps.