```sh
# Adding ppa to local repository
sudo add-apt-repository ppa:webupd8team/java
# Updating repository archives
sudo apt update
# Installing Oracle Java8
sudo apt install -y oracle-java8-installer
# Verifying the java installation
javac -version
# Setting Oracle Java8 as default (In case of multiple java versions)
sudo apt install -y oracle-java8-set-default
# Setting up environment variable (Also, add this to the `~/.bashrc` file to apply for next boot)
export JAVA_HOME=/usr/lib/jvm/java-8-oracle
export PATH=$PATH:$JAVA_HOME/bin
```