First, you need to add webupd8team Java PPA repository in your system. Edit a new PPA file /etc/apt/sources.list.d/java-8-debian.list
in text editor
sudo vim /etc/apt/sources.list.d/java-8-debian.list
and add following content in it.
deb http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main
deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main
Now import GPG key on your system for validating packages before installing them.
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EEA14886
Now use the following commands to update apt cache and then install Java 8 on your Debian system.
sudo apt-get update
sudo apt-get install oracle-java8-installer
Finally, you have successfully installed Oracle Java on your Debian system. Let’s use the following command to verify installed version of Java on your system.
java -version
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)
In Webupd8 PPA repository also providing a package to set environment variables, Install this package using the following command.
sudo apt-get install oracle-java8-set-default
References: https://tecadmin.net/install-java-8-on-debian/