Detect Java version

Description: Having a way of detecting a necessary Java version from the repo would be very handy, instead of needing to supply it. Many other setup-* Github actions support this. Perhaps this can be parsed from maven.compiler.target in Maven repos

[brunoborges]

There are so many ways for the Java version to be set in a Java project, that it really should be the developer responsibility to get that information, and pass it to the action.

Here’s how I do it:

https://github.com/brunoborges/aks-jvm-benchmark/blob/main/.github/workflows/maven.yml#L19-L27

I particularly see no good reason (only cons) for implementing any further on this.

[danielcompton]

Another source for the Java version is the .java-version file, used by jenv, as well as asdf’s .tool-versions.

Perhaps instead of automatically detecting the version and handling conflicts from different tools, you could allow setting the version from the file. For example

with:
  java-version: ‘.java-version’