Change effective on 21 September 2017
Heroku’s support for Java, Scala, Clojure, Gradle, and JRuby now includes support for OpenJDK version 9. To use this version of the JDK, create a
system.properties file in your application and put the following code in it:
After your next deployment, Heroku will install and run your app with OpenJDK 9. For more information, see the article on Heroku Support for Java in the Dev Center. For more information on JDK 9, see the official OpenJDK documentation.