Simple script that add Java support in update-alternative. Takes the latest folder in /opt/java as the reference.

update-alternatives-java.sh

#!/bin/bash

# First of all, we check if the user is root
if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root"
   exit 1
fi

update-alternatives --install /usr/bin/java java /opt/java/$(ls -tr | tail -1)/bin/java 1
update-alternatives --install /usr/bin/javac javac /opt/java/$(ls -tr | tail -1)/bin/javac 1
update-alternatives --install /usr/bin/javadoc javadoc /opt/java/$(ls -tr | tail -1)/bin/javadoc 1