I've got Oracle's Java 8 JVM installed, and on my system, the Firefox plugin is available through the Debian Alternatives System (which has the added benefit of allowing you to switch between JVMs) at /etc/alternatives/mozilla-javaplugin.so.
I've got Oracle's Java 8 JVM installed, and on my system, the Firefox plugin is available through the Debian Alternatives System (which has the added benefit of allowing you to switch between JVMs) at /etc/alternatives/mozilla-javaplugin.so.