It'll be documented somewhere in the JavaFX docs on the oracle web site, but it's probably easier to ask on the forum. I think I originally saw it on here somewhere.
If you're curious about whats available for an Object in B4j, in the IDE you can type Sub then the space bar, then Tab and you'll get a list of Objects, select one and you'll get a list of methods that are exposed for that Object. Same for B4a.