Is it Time for Functional Programming in Java?

Thank you Jacek,

lambdaj, like the other projects I mentioned, just tries to mimic what any decent language of the XXI century should offer out of the box. Since these libraries are the result of the effort of some "heroic" programmers who are tired of this lack in a mainstream language like Java, of course they cannot provide an ideal solution. So I just tried to quickly summarize their respective pros and cons.

Actually I am an happy Scala programmer since more or less an year, but very often (as probably it happens to the biggest part of us) I am obliged to stuck programming in Java. In all these situation the use of those libraries (with all their defects and flaws) are the only possible way to have some sort of functional programming feature in Java.

Cheers
Mario

Here's a blob of Erlang code that saves some object data into their Mnesia object database:

SaveFun = fun() ->

      ...do some DB saving logic here, e.g. insert some new records

               end,

mnesia:transaction(SaveFun).

 The last part "mnesia:transaction(SaveFun)" is the important one here. You are passing a function instance to another function as an argument. That function takes care of all the regular logic (open transaction, commit it, rollback in case of error, etc.). It's that type of reusability that is very useful.

Sure, you can do exactly the same by passing an instance of Runnable to a method, but it's 2-3 lines more of boilerplate code. It adds up.

Things get even more concise with closures combined with list comprehensions (another Erlang example):

[net_adm:ping(NodeName) || NodeName <- rpc:call(MasterNode,erlang,nodes,[])];

What this code does is call a remote Erlang node, asking it for its list of cluster nodes it knows. Then it passes that list into a list comprehension which executes a closure (in this case a ping of that node that establishes a connection to i.

Let's try to write this code in typical iterative Java

List<Node> nodes = masterNode.getNode();

for(Node node : nodes) {

    SomeNetworkLibrary.ping(node);

} 

 As I said, it quickly adds up. The ability to pass functions into other functions as arguments allows to build really nice tight, generic algorithms and the ability to do list comprehensions cuts down on number of lines of code significantly.

Now, that is said and done Erlang has a lot of other issues (it denies OO and makes everything immutable, so complex nested record manipulations are a major pain). But being exposed to it opened my eyes to what Scala tries to do, i.e. bring the best of both functional and OO programming together.

Foreign, yes. Compressed yes. It's a different language, obviously.

But once you get used to it (took me 2 weeks or so) then it reads as naturally as your more verbose Java code.

As I said, I didn't get into functional programming because it's the latest fad, but because I actually did a project in a language that supports it. Now I find myself thinking in this way when I write Java code and missing this type of concise, reusable constructs.

I think scala is the answer. It takes longer to morph java into a functional language than it does to simply change to a functional language.

I agree. All I want is a usable Eclipse plugin (that handles mixed Java/Scala projects with ease) and we're off running with Scala in a month. No more complaining from me about Sun wasting resources on JavaFX when their crown jewel needs some serious TLC instead.

I agree functional-wise you are better going straight to Scala if you have that option , but I implore the Java community, Sun , Oracale etc to get some JSR approved that addresses this concern properly in Java.

Given the amount of systems out there it would have massive benefits. The adoption of Scala will come but will not be anywhere near Java in I would say the next 5-10 years. I didnt completelty like BGGA but functionaly it was good and I would work with it. Blochs proposal just seems to short cut the syntax and you would end up declaring millions of interfaces in certain use cases ( see Forkjoin ).

Ok, I'm on board now with the Scala thing. It's got all those modern feature. I particularly like traits/mixins, multiple inheritance (I absolutely *hated* missing that since I left C++ 10 years ago).

I see great value in functional programming, and the rest of the features.

Scala doesn't suffer from a fanboy syndrome (eg. Ruby, Python) from what I can gage so far, and doesn't go reflection happy like Groovy.

Clearly, we have a winner here. Ok, so what's with the lack of Eclipse / Netbeans support? Is it or is it not possible to edit these files, debug them, and benefit from all those nifty source code management tools?

Back to the original topic - should we have functional programming in Java? Well, closures fell apart for Java 7, and one of Java's strong values is the fact that it's kept simple enough where mediocre programmers can remain effective. Perhaps there's pressure to keep Java accessible by cheap off-shore programmers from big companies (politics is preventing Java from evolving).

But who cares, Scala is just another, better javac.

I'm curious which language would be Scala's closest competitor in terms of being the best language?

Clojure, another language to investigate. At first glance, people seem to like Scala better.

But is Scala functional (enough) (no pun)?

http://enfranchisedmind.com/blog/posts/scala-not-functional/

Groovy looks done.

Rumors of Ruby based architectures getting replaced with Scala.

Python can't stand.

Any other contenders?

Interessing, that someone say javascript/python is prodecural not functional.

 Both languages have some elements and the possibility to do it. Look at united-coders.com/ for python. In javascript there are some libs (Functional) and some extensions in newser browsers.

I don't have an idea why the there is so much rumour now about functional programming.

Given the sample from http://en.wikipedia.org/wiki/Functional_programming#Coding_styles I can only say that it is far from my experience in practice. In very few cases I can find such clear (mathematic) relations.

What functions are used to manipulate an item before adding to target or returning as output usually depends on a series of conditions so it would not be efficient to write a code in a functional way.

I am pretty sure that a lot of Java programmers did excessive use of objects and classes in solutions that could have been easier with less objects and classes using just a few static classes with the appropriate methods dealing with the data.

So however am trying to find out how people see the big advantage in functional programming (style), I can't really find it. Maybe someone can help me se it...