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The RaspberyPi is great for learning Computer Science (as well as Engineering). If you already have a screen with a HDMI plug, a keyboard, and a mouse, you can can get started for less than $50–even less if you have a spare microSD card. I got a Pi 3 Model B+ in 2018 and started making some of the projects at BlueJ (which is already installed on Raspian). Below are my adapted projects.
In 2022 I got a Raspberry Pi4 400. Unfortunately, it is so new, the old gpio -v gave me the message “Oops - unable to determine board type… model: 19”
I found some help at https://pi4j.com/1.4/install.html. I followed the “Easy Method” which produced the pi4j-core.jar file that I needed. So BlueJ finds it, I copied it over to the proper directory:
sudo cp /opt/pi4j/lib/*.jar /usr/share/bluej/userlib/