According to a user report 64-bit OpenJDK requires the clflush instruction to work. clflush is removed to make rowhammer and sidechannel attacks more difficult. Whonix 14 will be 64-bit and so a workaround like running 32bit OpenJDK is needed as a workaround to preserve this protection.
TO-DO: Test instructions forinstalling 32-bit OpenJDK on a 64-bit Debian when an RC image is available.
If the following succeeds, change all OpenJDK installation documentation on the wiki to reflect it:
sudo dpkg --add-architecture i386
sudo apt-get update
sudo apt-get install openjdk-8-jre-headless:i386
sudo /usr/sbin/update-java-alternatives -s java-1.8.0-openjdk-i386