Simple, interesting Java libraries for a CS0 course?

You may be familiar with "CS1" and "CS2" classes, which are the first two college-level courses that someone would take on their journey of majoring in Computer Science, here in the United States (US). They typically focus on programming skills, and are followed by a 'data structures and algorithms' class.

"CS0" is an introduction to computer science intended to help get students ready for CS1 and CS2. They often (but not always) focus on programming. Since they're trying to cover the foundational programming concepts they sometimes (but not always) use graphical / block-based programming environments to help students learn the concepts (like if statements, loops, arrays, functions, etc) without having to deal with syntax errors. While that may help clarify the level of challenge that CS0 courses commonly target it's important to note that many CS0 classes are taught with textual languages (such as Python or Java).

I'm going to revise the CS0 course at the Community College where I teach and would love advice, hints, or pointers about the following:

What simple Java libraries do recommend, suitable for use in a CS0 level course, that do something the students will find interesting an engaging?

"Simple" applies both to the API (i.e., reasonably easy to code) and to the installation (ideally, works by including a single .JAR or something comparable)

By "Engaging" I mean something more interesting than the traditional System.out.println. Writing simple phone apps quickly and easily and running the app both on their desktop and on their phone would be _awesome_. Especially if it was easy to install. I.e., if you didn't have to install Android Studio and a simulator to get everything to work.

Some examples:

* "Simple Java Graphics Library" at https://horstmann.com/sjsu/graphics/ * "Java Bridge for App Inventor" at http://www.appinventor.org/jBridgeIntro