Setting the default JDK with the /usr/sbin/alternatives Utility

alternatives  creates, removes, maintains and displays information about the symbolic links comprising the alternatives system. The alternatives system is a reim-
       plementation of the Debian alternatives system. It was rewritten primarily to remove the dependence on perl; it is intended  to  be  a  drop  in  replacement  for
       Debian’s update-dependencies script.

1. Become the root user.
   /usr/sbin/alternatives needs to be run with root privileges. Use the su command or other mechanism to gain these privileges.
2. Set java.
   Input this command: /usr/sbin/alternatives --config java
   Set javac.
3. Enter this command: /usr/sbin/alternatives --config javac
   
   

Kaynak: https://access.redhat.com/documentation/en-US/JBoss_Enterprise_Web_Platform/5/html/Installation_Guide/sect-use_alternatives_to_set_default_JDK.html