jflex software package provides lexical analyzer generator for Java, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install jflex
jflex is installed in your system.
Make ensure the jflex package were installed using the commands given below,
$ sudo dpkg-query -l | grep jflex *
You will get with jflex package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Java |
| Package | jflex |
| Version | 1.4.3-3 |
| Description | lexical analyzer generator for Java |
| Sub Section | Java |