To follow this first session, please install the latest Java version on your machine.
Then open a command prompt (or terminal) and type java -version and press enter/return. You should see something similar to this:
java version "15.0.2"
Java(TM) SE Runtime Environment (build 15.0.2+7)
Java HotSpot(TM) 64-Bit Server VM (build 15.0.2+7, mixed mode)
If you see a different version, then your path is most likely wrong. If you don't know how to fix that, please ask someone :-)
Once that works, type jshell and press enter/return. You should see something similar to this:
| Welcome to JShell -- Version 15.0.2
| For an introduction type: /help intro
You are now ready to get going. Once you've had enough, type /exit and jshell will close.