Why is alternatives command used when installing Java on a Linux machine

Question

The below command is need when installing Java on a Linux machine (saw the command in a tutorial).

alternatives --install /usr/bin/java java /usr/java/jre1.         


        

Answer 1

It's not specific to Linux, only some of the distributions. It's better for maintaining multiple versions of the software or libraries and easily switch between them. Your applications are only pointing to the symbolic link, which you can easily switch any time and don't have to go through all the configurations of your applications. I don't know what the 20000 means, but here's the manpage: http://linux.about.com/library/cmd/blcmdl8_alternatives.htm (but you should have that in your system too)