I just merged a patch to master that drops JDK 7 support from Kudu's Java artifacts (i.e. the Java client, Spark bindings, etc.). The oldest supported JDK version is now JDK 8.
JDK 7 support has been deprecated since Kudu 1.5.0 (about a year and a half ago) so there's been ample notice that this change was coming. That said, if this change significantly impacts you, please let us know; there's still plenty of time before the next Kudu release to revisit this decision. Feel free to reply to this e-mail, or comment directly on KUDU-2099.