Monads for Java Programmer

http://irekjozwiak.com/entry/2009/06/13/Monads-for-Java-C---programmers.html

(>>=) bind

a1 >>= a2 = join (fmap a2 a1)

fmap _            Nothing       = Nothing

fmap someFunction (Just a)      = Just (someFunction a)
 

> fmap (+ 2) (Just 4)
Just 6

> fmap (+ 2) (Nothing)
Nothing

join Nothing         = Nothing
join (Just Nothing)  = Nothing
join (Just (Just x)) = Just x