> Firstly, only Java 8 is supported, so your build.sbt needs > to have some configuration in it that enables 1.8 only > support NONONONONONONONONO ! Who told

> Firstly, only Java 8 is supported, so your build.sbt needs > to have some configuration in it that enables 1.8 only > support NONONONONONONONONO ! Who told you that? If you don't compile on Jdk 9 with target/source 9 it just doesn't matter which JVM version you use they should be Downwards Compatible, especially OpenJDK 8 which actually Lambda uses.