Install on Linux Mint 19

[dave31175]

I'm trying to install on Linux Mint 19. When I try to install openjdk-7-jre, I receive:

Package openjdk-7-jdk is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'openjdk-7-jdk' has no installation candidate

I was able to install openjdk-8, but after installing Subsonic, I receive the dreaded 503 Service Unavailable error.

Any suggestions? Thanks.

[LRanger]

Subsonic runs for me using Oracle Java 8.