1. Download Java from here I have downloaded rpm in bin format.

2. Extract rpm from binary and then install it:

$ ./jre-6u5-linux-i586-rpm.bin
$ rpm -ivh jre-6u5-linux-i586.rpm

3. Make softlink to libjavaplugin_oji.so in your Mozilla Plugins directory after making sure that /root/.mozilla/plugins directory exists, else create the plugins directory first. Now as an example, if java is installed in /usr/java, this command will do the trick:

$ ln -s /usr/java/jre1.6.0_05/plugin/i386/ns7/libjavaplugin_oji.so /root/.mozilla/plugins

4. Restart firefox. Check if java is supported now. you can go here to test for its working.

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