Change effective on 20 July 2018
Heroku’s support for Java, Scala, Clojure, Gradle, and JRuby now includes the option of using JDK 8u181 or 10.0.2. To set the JDK version for an application, create a
system.properties file in the root directory of your project and put the following code in it:
For a more information on supported versions, see the Dev Center documentation for Java. For more information on OpenJDK 8u181, see the OpenJDK documentation for Java 8. For more information on JDK 10.0.2, see the OpenJDK documentation for Java 10.