The current version of raspbian installs jdk-11 (hard float) and that is just fine, if you have more that one version of java installed you could use update-alternatives tool to manage their use.

Then install JRuby see jruby.

jgem install picrate

Install samples, and configure geany ide (for PiCrate)

picrate -i
# or
picrate --install

or for no geany configuration

picrate -i Samples
# or
picrate --install Samples

Install processing libraries

# picrate -i Sound not currently working
picrate -i video # preferred over vanilla video for now

Creating Sketches from the GeanyIDE

See editors geany, for how to run sketches from a gui.

Running PiCrate sketch on RaspberryPI from geany editor