Java support upgrades Maven to 3.3.9
Change effective on 02 December 2015
Heroku’s Java support has upgraded the default version of Maven to 3.3.9. To upgrade to this version, create a system.properties file in the root of your application (or modify the existing file) and add this line:
maven.version=3.3.9
You may also select 3.0.5, 3.1.1 or 3.2.5. If you are already using an older version of Maven, you will not be upgraded to the new version by default. You must specify the version in system.properties to receive the upgrade.
For more information on Maven and its versions, see the Apache Maven documentation. See the Dev Center for more information on Heroku Java Support.