Java 8 for ubuntu18.04, Java SE 8 (LTS), Extended Support Until March 2025

sudo apt-get install oracle-java8-installer
sudo apt-get install oracle-java8-set-default
sudo update-alternatives --config java
sudo update-alternatives --config java
java -version
javac -version

At the end of this file, add the following line, making sure to replace the highlighted path with your own copied path:

sudo vim /etc/environment

JAVA_HOME="/usr/lib/jvm/java-8-oracle/jre/bin/java/"

echo $JAVA_HOME

/usr/lib/jvm/java-8-oracle/jre/bin/java/