The latest Jenkins 2.46.3 LTS apt package has the following dependency set: default-jre-headless|java8-runtime-headless
Where default-jre-headless depends on version 2:1.8 or higher (>= 2:1.8).
This dependency seems to be incorrect as, for now, this is only valid for the weekly Jenkins releases (which is incompatible with Java 7 and lower).
The 2.46.3 release notes also do not mention this change.
Because of this dependency Jenkins 2.46.3 cannot be installed on Ubuntu 14.04 as it lacks an official Java8 package.