#Add the following line to /etc/apt/sources.list:#
deb https://debian.opennms.org/ stable main
#Install GPG key of the repository:#
wget -O - http://debian.opennms.org/OPENNMS-GPG-KEY | sudo apt-key add -
#Update the package index:#
sudo apt-get update
#Install oracle-java8-installer deb package:#
sudo apt-get install oracle-java8-installer