A university professor that created the Modula-2 compiler sold by Borland, and was one of the Pizza compiler designers, which contributed to Java generics.
Not your regular university professor, rather someone with industry experience, specially in the Java world.
You forgot to also mention that he was the original author of the Java 5 compiler which Sun took over. He is definitely not a guy in an ivory tower, almost the exact opposite in fact. But ivory towers are not necessarily bad. It was precisely an ivory table that gave us Lisp and Haskell. Lisp's Garbage Collector was a big influence on the original Java. And Java's chief architect has specifically mentioned Haskell as his influence in the future of Java.
Truth be told there are plenty of those folks as well.
In European universities you aren't necessarily required to do outside work, so there are plenty that do the path, student, Msc student, PhD student, Professor, department chair, retirement.
In fact, I had a couple of occasions where good professors told me to just taste the professional world between getting the degree, and trying to pursue further academic life.
My second attempt at it, while at CERN, kind of did it for me.
So I do understand where the stereotype comes from.
Not your regular university professor, rather someone with industry experience, specially in the Java world.