How can I install Sun/Oracle's proprietary Java JDK 6/7/8 or JRE?

The Script way

Other ways view the full article at http://askubuntu.com/questions/56104/how-can-i-install-sun-oracles-proprietary-java-jdk-6-7-8-or-jre

If you're on a fresh installation of Ubuntu with no previous Java installations, this script automates the process outlined above if you don't want to type all that into a console. Remember, you still need to download Java from Oracle's website -- Oracle's links are not wget friendly.
Before using this make sure that this script is in the same directory as the .tar.gz file extension that you downloaded and there are no files that start with jdk-7 in the same folder. If there are, please move them out of the folder temporarily. Remember to make the script executable (chmod +x <script's file>).

#!/bin/sh

tar -xvf jdk1.8*  #Change by the you downloaded from oracle
sudo mkdir /usr/lib/jvm
sudo mv ./jdk1.7* /usr/lib/jvm/jdk1.7.0
sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdkx.y.z/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdkx.y.z/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdkx.y.z/bin/javaws" 1
sudo chmod a+x /usr/bin/java
sudo chmod a+x /usr/bin/javac
sudo chmod a+x /usr/bin/javaws

If you want to install the plugin for Firefox then add this to the end of the script:

mkdir ~/.mozilla/plugins
ln -s /usr/lib/jvm/jdk1.7.0/jre/lib/amd64/libnpjp2.so ~/.mozilla/plugins/
sudo /etc/init.d/apparmor restart