If you have code auto-completion in your IDE, then you are able to see available function calls associated to different implementations. This is a second source of reference when looking for additional functions. Another source, as pointed out by gotoloop is the source code. This is not the best but it is worth to explore it as it is quick and could resolve some immediate questions. You are also welcome to bring external libraries. For instance, if you find a Java solution in Stackoverflow, you should be able to use it in Processing.
Kf