Binary package “jflex” in ubuntu focal

lexical analyzer generator for Java

 It is also a rewrite of the very useful tool JLex which was developed
 by Elliot Berk at Princeton University. As Vern Paxon states for
 his C/C++ tool flex : They do not share any code though.
 .
 JFlex is designed to work together with the LALR parser generator CUP
 by Scott Hudson, and the Java modification of Berkeley Yacc BYacc/J
 by Bob Jamison. It can also be used together with other parser generators
 like ANTLR or as a standalone tool.