How to Install Java on Ubuntu

You can install either OpenJDK or Oracle JDK.
Steps to install Java 8 on Ubuntu 16.04.
Installing OpenJDK on Ubuntu is very easy you just need to run the following command.

sudo apt-get install openjdk-8-jdk

This command will both download and install the required packages.

If you want just the Java run time environment (JRE) then you can use the following command.

sudo apt-get install openjdk-8-jre

Installing Oracle JDK on Ubuntu
Script for installing Oracle JDK using apt-get is maintained by the third party, you can use that to install Oracle JDK or download the latest JDK from Oracle’s site and install it yourself.

Using apt-get

For installing using apt-get you need to add Oracle’s PPA (Personal Package Archive) then update the package repository using that information.

Use the following command to add PPA

sudo add-apt-repository ppa:webupd8team/java

Use the following command to update packages.

sudo apt-get update

Then for installing Java 8 use the following command.

sudo apt-get install oracle-java8-installer
Manually downloading and installing Oracle JDK

You can download the required JDK version from here - http://www.oracle.com/technetwork/java/javase/downloads/index.html

Then create a directory where you want to unpack the downloaded tar ball.

sudo mkdir /usr/local/java

Change directory to Downloads where tar ball will be downloaded by default and copy it to the created directory.

sudo cp -r jdk-8u151-linux-x64.tar.gz /usr/local/java

Then unpack the tar in the directory /usr/local/java using the following command.

sudo tar zxvf jdk-8u151-linux-x64.tar.gz

Setting JAVA_HOME environment variable and path
You need to set the JAVA_HOME environment variable so that the applications know the Java installation location.

Open the /etc/environment file using gedit.

sudo gedit /etc/environment

Add JAVA_HOME environment variable at the end of the file.

JAVA_HOME="/usr/local/java/jdk1.8.0_151"

Also append the path to /bin directory of your Java installation to the existing PATH variable in /etc/environment file.

:/usr/local/java/jdk1.8.0_151/bin 

Save and close the file. You need to reload it so that the changes are visible.

source /etc/environment
If you echo JAVA_HOME now you should get the path you set, try that using the following command.

echo $JAVA_HOME

If you have any doubt or any suggestions kindly drop a comment. Thanks!