This articles gives the exact steps needed to install jdk on debian based linux distributions… really helpful..
How to set JAVA_HOME in Debian based distros (Ubuntu/Linux Mint)
edit /etc/bash.bashrc file and include the following at the bottom
JAVA_HOME=/usr/lib/jvm/java
export JAVA_HOME
PATH=$PATH:$JAVA_HOME/bin
export PATH
(Source: zimbio.com)