Extenuating circumstances require me to run more than one version of Java JRE for work. Instead of using packages from the distro, I got the .tar.gz’s right from Oracle. I had to manually add the plugin to Firefox. Then, I extracted both JRE into /opt/java, added /opt/java to my path and made symlinks:
carl@carlworkstation:/opt/java$ ls -l
total 8
lrwxrwxrwx 1 carl carl 20 Jul 1 15:01 java -> jre1.7.0_80/bin/java
lrwxrwxrwx 1 carl carl 20 Jul 7 16:05 java7-java -> jre1.7.0_80/bin/java
lrwxrwxrwx 1 carl carl 22 Jul 7 16:49 java7-javaws -> jre1.7.0_80/bin/javaws
lrwxrwxrwx 1 carl carl 20 Jul 19 14:52 java8-java -> jre1.8.0_92/bin/java
lrwxrwxrwx 1 carl carl 22 Jul 7 16:06 java8-javaws -> jre1.8.0_92/bin/javaws
drwxr-xr-x 6 carl carl 4096 Apr 10 2015 jre1.7.0_80
drwxr-xr-x 6 carl carl 4096 Apr 1 00:17 jre1.8.0_92
I wrote a little helper script which I use as the default application in Firefox for this, using zenity (actually I use Palemoon, but same difference).
#!/bin/bash
command=$(zenity --list --text "Is linux.byexamples.com helpful?" --radiolist \
--column "Pick" --column "Opinion" TRUE /opt/java/java8-javaws FALSE /opt/java/java7-javaws );
$command $1
Java Selector