GNU/Linux Ubuntu 20.04 Installing Java Guide
This tutorial will guide you step-by-step on How to Install Oracle Java SE on Ubuntu 20.04 Focal LTS GNU/Linux.
And the Oracle Java SE Ubuntu Focal Release includes:
- Java Runtime Environment to Run Java Software
- Java Development Kit to Develop Java Software
Moreover, the Java OpenJDK (Open Java Development Kit) is the Free and Open Source Implementation of the Java Platform, Standard Edition (Java SE).
Where the Oracle JRE/JDK is based on the OpenJDK Source Code. In Addition, it contains Closed-Source Components.

GNU/Linux Ubuntu 20.04 Java SE Installation Guide