I've written two new blog articles that might be of interest:
I recently implemented a read-eval-print-loop (REPL) for JavaFX. A REPL (also called a command shell) allows you to type in expressions, have them be immediately evaluated, and the result displayed. This is very useful for experimenting with or learning a language.
It is actually somewhat tricky to make declarations in one command "visible" in future commands, at least in a language with static name-lookup and static typing, like JavaFX. This companion article talks about some of the implementation and API issues of REPLS and scripting in general, including some limitations of JSR-223 (javax.script).