steps to upgrade java from 1.6 to 1.7

I am using Bitnami SOLR 3.6.1 stack
It has jdk 1.6 installed.
I also installed jdk 1.7 simply running sudo apt-get install openjdk-7-jre
The java version is still showing 1.6
How do I actually upgrade.
When I run the update-java-alternatives -l, it doesn't show 1.6. It just shows 1.7
But 1.6 is up and running and is being referred.
What changes I need to do for it to refer to 1.7