This is how we install Oracle Java. It uses different repository than JDK9 and JDK8

Import key

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 73C3DB2A

Install Java

echo "deb http://ppa.launchpad.net/linuxuprising/java/ubuntu xenial main " | sudo tee -a /etc/apt/sources.list.d/linux-uprising_java.list
echo "deb http://ppa.launchpad.net/linuxuprising/java/ubuntu xenial main " | sudo tee -a /etc/apt/sources.list.d/linux-uprising_java.list
sudo apt update
sudo apt install oracle-java10-installer

Reference:

“Linux Uprising” team Oracle Java Option 1: Easy Installation (PPA)