CODEWITHSUNDEEP
javafunctional-programming
user1172468
user1172468

Reputation: 5464

Is there a java library for function programming?

Has anybody written a library in java that provides mapping functions (such as mapcar from lisp).

I saw this post and few others (such as this one this one), but sadly nothing that I could consider mainstream and/or usable.

Upvotes: 1

Views: 659

Answers (2)

C. K. Young
C. K. Young

Reputation: 223023

You'll be looking forward to Java 8, then! It will have Project Lambda included, which has a much, much nicer syntax for closure-like anonymous classes.† Example:

Iterable<String> strs = ...
Iterable<String> downCased = strs.map(s -> s.toLowerCase());

Any interface with one method (or abstract class with one abstract method) can use this syntax, including Guava's Function and Predicate (though Java 8 has its own Mapper and Predicate interfaces, so these are usable out of the box). In this case Iterable.map is a new extension method that takes a new interface type called Mapper.

If you'd like more examples of Java 8 lambdas, just ask!

† All the usual restrictions of anonymous classes still apply, including that local free variables must be "effectively final". This means you don't have to explicitly tag the variable as final, but you're still not allowed to alter the value.

Upvotes: 2

Tom Anderson
Tom Anderson

Reputation: 47183

There are a few. They are usually described as something like "functional programming in Java" libraries rather than by reference to LISP.

At my company, the functional programming druids settled on Functional Java as their preferred library, although there is a significant and vocal minority who prefer the functional-esque provisions in Guava.

Guava is a very mainstream and popular library; it's firmly in the "nobody got fired for using" category. FJ may be less well known, but we're using it pretty happily. We've even forked it so we can help improve it.

Upvotes: 6

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