Change effective on 04 February 2019
Heroku’s support for Java has been updated to use JDK 8u201 by default. For apps configured to use Java 7, the default is now 7u201. For apps configured to use Java 11, the default is now 11.0.2. All other default versions remain the same.
The default Java memory options for all JVM versions have been updated to exclude the
Xms (minimum heap) option. For more information, see the Dev Center article on Java Support.