Based on the image 'xxBedy/postgres-pljava/9:4' but using openjdk as oracle jdk is not redistributable without first accepting the end-user license.
Furthermore, this image has been optimized to be as small as possible. The aforementioned image this was based on currently sits at 1.4GB. This image, after the various optimizations made (we're not squashing), is just shy of 300MB.
Source can be found here: https://github.com/cdancy/postgres-pljava-openjdk