Intall Oracle JDK 8 in Ubuntu

Ubuntu comes with OpenJDK by default. You may need to remove OpenJDK first and install Oracle JDK as most of Enterprise apps use Oracle JDK.

To Remove OpenJDK

To Remove OpenJDK in Ubuntu, use the commands below:
```
  sudo apt purge openjdk-*
```

To Install Using Personal Package Archives (PPA)

To add webupd8team PPA as there is not official Oracle PPA, use the commands below:
```
  sudo add-apt-repository ppa:webupd8team/java && sudo apt update
```
To install Oracle Java Jdk 8, use the commands below and you need to accept Oracle license aggreement when asked :
```
  sudo apt install oracle-java8-installer
```
- If you’re behind a Enterprise firewall that blocks some of the redirects required to download the Oracle Java archive, you can download the JDK tar.gz archive manually and place it under /var/cache/oracle-jdk8-installer - then, installing the “oracle-java8-installer” package will use the local archive instead of trying it to download it itself.

To automatically accept the Oracle license, use below command if you did not accept it when you install for first time:

  echo oracle-java8-installer shared/accepted-oracle-license-v1-1 select true | sudo /usr/bin/debconf-set-selections  

To automatically set up the Java 8 environment variables, you can install the following package using below command:
```
  sudo apt install oracle-java8-set-default  
```
- If you’ve already installed oracle-java7-set-default, they will be automatically removed when installing oracle-java8-set-default (and the environment variables will be set for Oracle Java 8 instead).

To remove Oracle JDK and Install OpenJDK again, use below command:

  sudo apt remove oracle-java8-installer && sudo apt install openjdk-8-jdk

To Install from Oracle Website

Download latest version of Oracle JDK from Oracle Website.For Java 8 and 64 bit linux, the file name would be: jdk-8u101-linux-x64.tar.gz.
Copy the downloaded JDK file to a directory where you want to install the JDK. I use /apps/java/jdk-8u101-linux-x64.tar.gz.
Open terminal window and navigate to the directory where you copied the downloaded file. Then type the command to Uncompress it
```
  tar -xvf jdk-8u101-linux-x64.tar.gz
```
The JDK 8 package is extracted into ./jdk1.8.0_101. Jdk naming convention changes often. So, Create a softlink to avoid naming issues
```
  ln -s jdk1.8.0_101 jdk8
```

Now move the JDK 8 directory to /usr/lib

  sudo mkdir -p /usr/lib/jvm
  sudo mv ./jdk8 /usr/lib/jvm/

Now run below commands to assign Oracle JDK a priority of 1, which means that installing other JDKs will replace it as the default. Be sure to use a higher priority if you want Oracle JDK to remain the default.

  sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk8/bin/java" 1

  sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk8/bin/javac" 1

  sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk8/bin/javaws" 1

Correct the file ownership and the permissions of the executables:

  sudo chmod a+x /usr/bin/java

  sudo chmod a+x /usr/bin/javac

  sudo chmod a+x /usr/bin/javaws

  sudo chown -R root:root /usr/lib/jvm/jdk8

Run Below commands to select default executables for java/javac/javaws:

  sudo update-alternatives --config java

  sudo update-alternatives --config javac

  sudo update-alternatives --config javaws