As I'm sure you know, functional programming is a style and you can use it for any of the languages you mentioned (yes, including Java - objects are a poor man's closure but closure's are a poor man's object) [1]. One thing that might help is to try using functional idioms in the languages you know. Then you'll appreciate the syntatic help that "real" functional provide for that style.

[1]http://people.csail.mit.edu/gregs/ll1-discuss-archive-html/m...