Debian 8 alias Jessie ships with OpenJDK 7 which is fine in many cases. But sometimes you need a more recent version.
In that case you can use the ubuntu ppa archives as install source.
Just type these commands in the console of your Debian system and it should install just fine, also providing automatic security upgrades as they become available.
echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main" > /etc/apt/sources.list.d/webupd8team-java.list echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main" >> /etc/apt/sources.list.d/webupd8team-java.list apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EEA14886 apt-get update apt-get install oracle-java8-installer java -version