GNU/Linux KDE Neon Installing Java OpenJDK 21 – Step by step Guide
Install Oracle-Sun OpenJDK 21 LTS JRE/JDK in KDE Neon LTS 64-bit GNU+Linux desktop/server.
And Java OpenJDK (Open Java Development Kit) is a Free and Open Source Implementation of the Java Platform, Standard Edition (Java SE).
Furthermore, the Oracle Java JDK/JRE is based on the OpenJDK Source Code. In Addition, it contains Closed-Source Components.
Finally, OpenJDK 21 is the fourthJava Long Term Support Release.

1. Terminal Getting Started Guide
How to Quick Start with Command Line on KDE Neon GNU/Linux:
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