ecj-gcj software package provides standalone version of the Eclipse Java compiler (native version), you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install ecj-gcj
ecj-gcj is installed in your system.
Make ensure the ecj-gcj package were installed using the commands given below,
$ sudo dpkg-query -l | grep ecj-gcj *
You will get with ecj-gcj package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Java |
| Package | ecj-gcj |
| Version | 3.11.0-7 |
| Description | standalone version of the Eclipse Java compiler (native version) |
| Sub Section | Java |