Generally you can use 32bit libraries and binaries within a 64bit Linux system, but you need to have all the dependencies in 32bit as well for that to work. Not sure what versions of Java exist for armhf (32bit) or aarch64. There is also support in Armbian which has Debian and Ubuntu images for the Pine64 (make sure to read the notes for configuration hints), that is what I use atm for my boards: https://www.armbian.com/pine64/. As far as I know Oracle has JAVA for ARM:
http://www.oracle.com/technetwork/java/j...33151.html
http://www.oracle.com/technetwork/java/j...33151.html
Come have a chat in the Pine IRC channel >>