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.

Suspicion

sbt should just uses what is on the JAVA_HOME If you are sure you do not have Java 16 installed then it shouldn't use that, sbt doesn't download JDKs. – Anderer

If it is using Java 16 then its definitely installed somewhere. Check your java installation folder which can be found by following which java. You can set JAVA_HOME or use sbt -java-home <path/to/jdk> to use specific jdk. – Winery

SET JAVA_HOME=C:/Program Files/Java/jdk-16.0.1 <next line> sbt – Lenardlenci

Answer 1

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://mcmap.net/q/1285138/-how-to-set-java-version-for-sbt

Grandam

Answer 2

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")

Voluble

if both javacOptions and JAVA_HOME are set, sbt will use JAVA_HOME – Sheri

-source X will not help if a method becomes removed in your current VM (but was present in jdk X). – Belldame

Answer 3

To handle your installed jvms you can use Jenv.

To install jenv:

git clone https://github.com/jenv/jenv.git ~/.jenv
echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bash_profile

echo 'eval "$(jenv init -)"' >> ~/.bash_profile

Then, you can add your intalled jvms. In Mac, if you have installed them via brew you can find those in: /Library/Java/JavaVirtualMachines.

Then add them to jenv:

jenv add /Library/Java/JavaVirtualMachines/adoptopenjdk-11.jdk/Contents/Home 
jenv add /Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home 

You can see the available jvms in jenv:

you can set the default jvm with the command:

jenv global 1.8.0.121

Then, execute sbt in some of your projects and you should see that jvm as the jvm that sbt is using.

Rubio

I did not know about this thing, Its great tool – Grandam

I'd like to use jabba. I think that is very similar to jenv at this point.. – Gerik

Answer 4

Another option which worked for me is to add the version of java you want to be used to the front of your terminal PATH environment variable. Since I used homebrew to install openjdk, I used the path they suggested resulting in the following path to use openjdk version 11.

export PATH="usr/local/opt/openjdk@11/bin:$PATH"

Note - the openjdk path I used I think is just the homebrew symlink to the actual java installation which is in /Library/Java/JavaVirtualMachines. You could probably just use that actual path but I didn't test it.

Edieedification

I do believe that setting the JAVA_HOME variable is a better option. I just wanted to give this option in case other things don't work for someone. – Edieedification