if you really wish - you can change the bootstrap path and allow changing env() for whatever reason you want to (likely via copy on write). If you don't wish to do that feel free to spawn a child process with whatever env you desire, then redirect/join sys in/our/err (0/1/2)

Those are trivial things in around 100 lines of code and have been available since System.getenv() got back (it used to be deprecated and non-functional prior Java 1.5 or 2004)