Disclaimer: some do consider this a war like emacs/vim. I don't.
I'll quote you on this: "I'm looking for something that allows students to get up and running relatively quickly and easily with something small yet meaningful".
From this: JavaFX. Along with IntelliJ, and Scene Builder, students can build a GUI very, very quickly. The FXML file which ...
Instead of a System.in/out based dialog, you may consider a Pane containing
a Canvas for drawing
a TextField for user input.
Here is a sample program (hard-coded constants, to keep it short):
I'm going to suggest that you don't use either Swing or JavaFX for an AP CS course. Instead, I'm going to suggest that you use Princeton's Standard Draw library. It does a great job of abstracting all of the ugly canvas and window setup that traditionally comes along with Swing or JavaFX.
I have leveraged their library for multiple projects throughout the ...
Like everything else in programming, it's a mix of tradeoffs:
Benefits of Swing: There are a metric ton of tutorials and examples on the web. It still has a very active community here on Stack Overflow.
Downsides of Swing: It's old, and it looks old. It's not being actively developed anymore. (But it's not deprecated either.)
Benefits of JavaFX: It's new(er)...