http://tipsonubuntu.com/2016/07/31/install-oracle-java-8-9-ubuntu-16-04-linux-mint-18/
Quick Tutorial for Beginners The easily install Oracle Java JDK8 or JDK9 in Ubuntu 16.04 or Linux Mint via PPA.
WEBUPD8 team are maintaining a PPA repository with installer scripts for the latest Java 8 and 9, that automatically Downlo Ads The Java archive from Oracle website and sets up everything for you.
1. Add the PPA.
Open Terminal (CTRL+ALT+T) and run the command:
sudo add-apt-repository Ppa:webupd8team/java
Type in your password when it asks and hit Enter.
2. Update and install the installer script:
Run commands to update System Package index and install Java Installer script:
sudo apt update; sudo apt install Oracle-java8-installer
You could replace Oracle-java8-installer with Oracle-java9-installer to install Java 9.
While the install process is have to accept Java license to continue downloading & installing Java binaries.
3. Check the Java version
To check the Java version after installing the package, Run command:
Javac-version
4. Set Java Environment variables
The PPA also contains a package to automatically set Java environment variables, just run command:
sudo apt install oracle-java8-set-default
For Java 9, install the package Oracle-java9-set-default instead.