20100126: Functional Java

Starting to explore Functional Java, which have been on my radar for quite a long time. Of course, the Java syntax without syntactic sugar for closures does not help in accelerating understanding of what's going on particularly in the fj.control.parallel package which contains the most interesting stuff to do concurrent computations.

What I am trying to do is to parallelize maven builds using this framework:

• I have a standard function that runs some maven build and produces a result in the form of a return value (0 for success). This maven build maybe dependent on some other builds so has as its input a list of the return values of those dependent builds. This function is a standard java method, something like:

  
    public Integer maven(List<Integer> prerequisites) { ... }
  

• This java method is naturally wrapped into a function object using standard F constructor: previous

  
    private F<List<Integer>, Integer> mavenF(final int buildId) {
      return new F<List<Integer>, Integer>() {
      public Integer f(List<Integer> a) { return maven(a); }
       };
     }
  

• Then what I want is to chain those functions using Promise objects and concurrent computation. A Promise is like a java Callable (from java.util.concurrent package) on steroids: It is actually a Monad, so it can be composed using standard monadic bind() operator, it can lift plain functions into promises-taking and returning functions, and overall can dispatch computation of a promise lazily using some kind of parallelization-strategy object that returns some value.