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.
update-alternatives: using /usr/lib/jvm/jre1.7.0/bin/java to provide /usr/bin/java (java) in auto mode so it seems I did that part right.
It might have something to with environmental variables, e.g. JAVA_HOME and PATH but I'm not sure how to set them.