How to set Java version for SBT

Question

I am trying to run a scala program, in which there are errors with Java 16. My colleague is using Java 15, and all is fine. When i type java -version in my terminal it says i am using Java 15. However, when i run sbt run -v, it says it is using Java 16, and thus the program throws errors.

I am seeing people talk about this sbt-extra thing, but not a whole lot of explanation on how to use it. I do not even have Java 16 installed on my Mac, so I am really confused as to why SBT says this.

Answer 1

The best way is to do this via the build.sbt file so then it's specific to just that project not your entire local environment. I.e. add the following to build.sbt:

  javacOptions ++= Seq("-source", "11", "-target", "11")

Answer 2

Add this to ~/.bash_profile, ~/.bashrc or ~/.zshrc (depending on shell preferences/OS), or just run this before running sbt in a terminal:

export JAVA_HOME=/Library/Java/JavaVirtualMachines/adoptopenjdk-11.jdk/Contents/Home

It's better though to do this per-sbt project via build.sbt as per this answer: https://stackoverflow.com/a/76456295/1586965