JFlex is a lexical analyser generator for Java written in Java.  It is
also a rewrite of the tool JLex (Berk 1996) which was developed by
Elliot Berk at Princeton University.  As Vern Paxson states for his
C/C++ tool flex (Paxson 1995): they do not share any code though.

WWW: https://www.jflex.de/