> there will come a time when one branch will be used to test the jump from 17 to 24 or something like that, so you'll work on that, but also switch back to the master branch when a colleague needs some help there.

But can you not just install 24 on your dev box and use that to work on either branch, maybe with -source/-target arguments? It never used to be a problem to develop with a newer JVM even if it was an older project.

Note: Java compiler versions from 9 onwards have lost the ability to -target 1.5 and earlier.

Sometimes you still need Java 8 to compile for super old programs — think decades old IoT devices too small to handle newer JVMs that you still need to do the occasional minor update for.

But really sdkman is just nice to be able to quickly install and quickly switch jvms without worrying about any opinions the os package manager may have. If I want an old jre8, do I need to fuss around with finding the right package repo for my arch etc, or should I just use sdkman and be done with it.

Ideally, yes. In the real world? Nope. The longer you work one some project, the bigger the chance you will run into some edge case determined by the major version of the JDK. It just happens.

Even if you do all developing on the latest LTS, you will want to be able to switch to whatever version is running on the dev or prod application servers to replicate a bug as closely as possible.

By the way, you are ignoring the case I mentioned where a JDK bug happened between one minor version and the next.