Command to give a list of JREs installed on the system

Question

Is there any command which would list down all the JRE versions and releases installed on a system?

Answer 1

To list all the registered JRE (in a file called "jre.txt") on a Windows machine :

start /w regedit /e jre.txt 
   "HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment"

Answer 2

On ubuntu and some other linuxes they're mostly in /usr/lib/jvm. You can also check with

for x in $(echo $PATH | tr ':' ' '); do ls -asl $x | grep java; done

which will also show you all the pretty softlinks. There's probably a nicer way to do this that hopefully some kind person will post :)