scala-cli, one of the superpowers in the Scala ecosystem, is a versatile tool for running Scala scripts. It has a ton of options to play with. One of the arguments you can pass to scala-cli is to specify the JVM version to run a script under, which is as follows:
scala-cli --jvm 17 my-script.scala
When done so, scala-cli first looks for JDK installed in the system1, if not found, downloads the specified JVM using Coursier. It does not consider the JVM installed via package/version managers like sdkman.
$ java -version
openjdk version "17.0.13" 2024-10-15 LTS
OpenJDK Runtime Environment Zulu17.54+21-CA (build 17.0.13+11-LTS)
OpenJDK 64-Bit Server VM Zulu17.54+21-CA (build 17.0.13+11-LTS, mixed mode, sharing)
$ which java
/Users/***/.sdkman/candidates/java/current/bin/java
$ scala-cli --jvm 17 collect.scala
<download progress appears and disappears on download completion>
Downloading JVM zulu:17
<program output>
As you can see, scala-cli downloads the JDK 17 despite being installed (via sdkman). Now, the question is where does scala-cli install the downloaded JDK?
It does not install in the system path nor in any of the folders under the user’s home directory like ~/.cache or ~/.coursier. Instead, here is where it is downloaded and installed:
- Downloaded to
~/Library/Caches/Coursier/v1/https/cdn.azul.com/zulu/bin/zulu17.56.15-ca-jdk17.0.14-macosx_aarch64.tar.gz - Installed2 to
~/Library/Caches/Coursier/arc/https/cdn.azul.com/zulu/bin/zulu17.56.15-ca-jdk17.0.14-macosx_aarch64.tar.gz/zulu17.56.15-ca-jdk17.0.14-macosx_aarch64
That I found out after a long haul of investigation. But isn’t there a programmatic way to find it out? There is.
$ scala-cli --jvm 17 -e 'println(sys.props("java.home"))'
/Users/****/Library/Caches/Coursier/arc/https/cdn.azul.com/zulu/bin/zulu17.56.15-ca-jdk17.0.14-macosx_aarch64.tar.gz/zulu17.56.15-ca-jdk17.0.14-macosx_aarch64/zulu-17.jdk/Contents/Home
Courtesy of Seth Tisue in the Scala Discord channel.
UPDATE: @Gedochao shared in the Scala Discord channel a straight forward alternative to find out the JDK installation path:
cs java-home --jvm 17
AFAIK, neither scala-cli nor coursier provides a way to manage the JVMs. So, if you want to uninstall the downloaded JVMs, you can do so manually by deleting the folders mentioned above.
