1. Install Java6 SE or JRE from here.
2. Find your firefox installation. Mine was in /usr/lib/firefox-3.0.12
If you want to find out where your installation is, type:
grep 'LIBDIR' /usr/bin/firefox
You should see something like:
The LIBDIR variable has the location of the firefox installation.
3. Find the location of libnpjp2.so in your java installation.
Mine was in jdk_install_dir/jre/lib/amd64/libnpjp2.so
4. Change to the /usr/lib/firefox-3.0.12/plugins directory.
5. Create a symlink to your libnpjp2.so file.
ln -s jdk_install_dir/jre/lib/amd64/libnpjp2.so libnpjp2.so
Your plugins directory will now have a symlink named libnpjp2.so
6. Open firefox and type:
You should see something like the following:
Java(TM) Plug-in 1.6.0_14
File name: libnpjp2.so
The next generation Java plug-in for Mozilla browsers.
You can further test your java installation at the following sites:
That's it! :)
References: 1 and 2.