Add the below details after installing java in your system:
JAVA_HOME=/opt/jdk1.7.0
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
JRE_HOME=/opt/jdk1.7.0
PATH=$PATH:$HOME/bin:$JRE_HOME/bin
export JAVA_HOME
export JRE_HOME
export PATH
JAVA_HOME=/opt/jdk1.7.0
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
JRE_HOME=/opt/jdk1.7.0
PATH=$PATH:$HOME/bin:$JRE_HOME/bin
export JAVA_HOME
export JRE_HOME
export PATH
If you got any issues with eclipse please see the below link:
http://stackoverflow.com/questions/26211098/eclipse-is-unable-to-find-jvm-in-ubuntu-12