The easiest way to install Oracle Java (JDK) in Ubuntu is to use the WebUpd8 PPA. A PPA (Personal Package Archive) is a special software repository for uploading source packages to be build and published as an APT repository by Launchpad. This PPA will download the required files from Oracle and install JDK7 / JDK8 / JDK9.

The steps:

• Login to Ubuntu server.
• sudo apt-add-repository ppa:webupd8team/java

The apt-add-repository command add the ppa to the current repository. You will be prompted with information message about installation instructions with the detail url. You need to press ENTER key to continue the process to add the repository.

• sudo apt-get update

This will update the package list from the repositories and update them to get the latest versions of the packages and their dependencies. It will update all repositories and PPAs.

• sudo apt-get install oracle-java8-installer

This command will start the installation process, you will be prompted to accept the license agreement. Run sudo apt-get install oracle-java7-installer if you want to install JDK7 instead. This process will take sometime to finish depending on your connection speed. And if everything runs well you’ll get Java installed at the end of this process.

• java -version

This command return the version of the installed JDK. In this case it should return something like:

java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

The JDK8 will be installed in the /usr/lib/jvm/java-8-oracle directory. If you need to define the JAVA_HOME environment variable then it should be directed to this directory.