Starting from the official openjdk images, these Dockerfiles modify each JRE’s java.security settings to set the DNS TTL to 60 seconds and to use /dev/urandom* as an entropy source.
* Actually, it's using /dev/./urandom instead of /dev/urandom. This is the same thing, but it's working around a “feature” of the JRE that looks for the string /dev/urandom and switches it back to /dev/random. The only references to that behavior I can find are for Java 5 and 6, but in an abundance of caution, we're working around it in these Java 8 images too.