Recently with my ruby-processing projects I have been experimenting with using graalvm. Then I thought I would like to try it out with vanilla processing (particularly processing-4.0a3), it used to possible to just replace the processing pre-installed java with a symbolic link to your chosen jvm. Currently this is not possible with the processing ide, however if you are prepared to use processing-java it will work. Or better still you can use the atom editor:-
for the benefit of anyone interested in using the atom editor with processing I have written a wiki entry.