How to set environment variable JAVA_HOME that will be saved on exit?

Add to /etc/profile.local:

export JAVA_HOME=/usr/java/latest

That way it will be set for all users and will be independent of the release or patch-number. /usr/java/latest is a link to the latest installed version and exists since JDK/JRE 1.6

Set environment variables in ~/.profile, e.g. by adding this line:

export JAVA_HOME=/usr/java/jdk1.7.0_05