Basically, this library gives you the ability to strictly define a one method interfaceon the fly with support for the method to take up to 20 defined type paramaters, a defined return type or just as void. After 20 parameters ( who needs that many? ) we can use RU or VU for undefined and unlimited amount of parameters.
It's amazing that nobody actually got around to write something so basic and simple!
I have supplied threeClosure.java implementations (actually made a couple more but were dismissed), v0(version 0), v1and v2. My favourite of the three isv1though, but have a look at v2 as well which is a bit more dynamic, whereas v0 and v1 are fully static.