This is a custom buildpack of AdoptOpenJDK Buildpack which installs the Eclipse OpenJ9 VM AdoptOpenJDK11.
Replace the default Heroku Java buildpack
$ heroku buildpacks:set https://github.com/maatuss/openj9-buildpack.git
$ heroku buildpacks:add heroku/java
$ git push heroku master
Create a file system.properties at the root of your project
adoptopenjdk.version=<version>
adoptopenjdk.release=<release>
MIT