GNU/Linux Ubuntu 18.04 Install OpenJDK Guide
How to Install Oracle Java OpenJDK JRE/JDK on Ubuntu 18.04 Bionic LTS GNU+Linux desktop.
And the Ubuntu 18.04 OpenJDK Installation is a Free and Open Source Implementation of the Java Platform Standard Edition.
Oracle Java JDK/JRE Installation is based on the OpenJDK source code. In Addition, it contains Closed-Source Components.
Possibly see also: How to Download and Install Oracle JDK on Linux Distros.

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1. Terminal QuickStart
How to QuickStart with Command Line on Ubuntu
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