How Install Oracle JDK 8 On Ubuntu

Download jdk-8uXXX-linux-x64.tar.gz from Java SE Development Kit 8 Downloads

Unzip jdk-8uXXX-linux-x64.tar.gz to /usr/lib/jvm

sudo mkdir /usr/lib/jvm
sudo tar -zxvf jdk-8uXXX-linux-x64.tar.gz -C /usr/lib/jvm

Configure JDK

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8.0_XXX/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8.0_XXX/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.8.0_XXX/bin/jar 300   
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.8.0_XXX/bin/javah 300   
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.8.0_XXX/bin/javap 300 

#if you have multiple java version installed, you have to run this command
sudo update-alternatives --config java

Test

java -version