Install openjdk8

Execute the following commands in order

sudo apt-get update 
sudo apt-cache search openjdk

Note: Select any suitable package from the top. This documentation selects the openjdk-8-jdk

sudo apt-get install openjdk-8-jdk

Prepare your system for jenkins in ubuntu

Execute the following commands

wget -q -O - https://pkg.jenkins.io/debian/jenkins-ci.org.key | sudo apt-key add -
echo deb https://pkg.jenkins.io/debian-stable binary/ | sudo tee /etc/apt/sources.list.d/jenkins.list
sudo apt-get update

Before executing install of jenkins lets try to find the possible jenkins versions available

sudo apt-cache madison jenkins

Note: In this documentation 2.138.3 will be used

Installing Specific Version of Jenkins

sudo apt-get install jenkins=2.138.3 -y

Note: Follow this steps to install any LTS version of jenkins