Fair enough. But as a simple example, neither openjdk6 nor openjdk7 are available in my Ubuntu distro (16.04, not even bleeding edge).
And that's why I use Azul Zulu JDK :-)
The Azul Zulu team still supports Java 6 (at least I haven't hear the drop of support).
So +1 for drop support for Java 6, and -1 for drop support for Java 7.
Still unconvinced of a strong reason to keep support for Java 7. My +1 for Java8+.
Yes, there are not strong reasons to keep support for Java 7 (apart that it's still widely used), but there are not strong reasons to drop support for Java 7 neither.
It looks like the java implementation mentioned scram-sasl supports Java 7, and BTW the Base64 class of Robert Harder is in PgJDBC, but hey if you convince the project maintainers to move to Java 8+ I'm not against it :-) as I said the project is ultra-conservative for better or worse.