Why doesn't java -version return anything with Oracle's JRE 7?

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http://askubuntu.com – I've been following these steps and got up to the check version of new JRE installation part but java -version doesn't return anything. I have run sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jre1.7.0/bin/java and it returned update-alternatives: using /usr/lib/jvm/jre1.7.0/bin/java to provide /usr/bin/java (java) in auto mode so it's seems I did that part successfully. It might have something to with environmental variables, e.g. JAVA_HOME and PATH but I'm not sure how to set them. (HowTos)