Maven builds default to version 3.5.2; the most recent version is 3.6.0. It would be nice to select your own version whether you team has run ahead of what is available in Travis, or you haven’t had an opening to catch up.
A co-worker introduced me to a tool that you may be able to implement easily for Maven: Maven Version Manager http://mvnvm.org. I don’t know if there is an equivalent tool for Gradle/SBT/et al.