Most proposals state that it’s not the syntax that matters, it’s the semantics. While this is undoubtedly true, syntax is the first thing a programmer will see and judge the feature by. If the syntax isn’t self-explanatory enough, it will be a cause of rejection, and the feature will not be used as it could have been. So I do believe syntax is a key point of the future Java closures feature, and in this respect I tend to favor Mak Rheinhold’s proposal or the FCM proposal rather than BGGA.

Mark Rheinhold’s proposal

Project Lambda

LambdaJ partially alleviates the need for closures by allowing the manipulation of Collections in a way that doesn’t require iterating through the items. For example you could write

forEach(personInFamily).setLastName("Fusco");

with personInFamily being a List of Person, and setLastName being a method on the Person class. Actually, forEach returns a proxy that implements both the Iterable interface and the methods of the collection items’ class (Person in this case). A call to any of these methods is then propagated to each member of the collection.

As you can see, LambdaJ uses the DSL-style notation that mock frameworks introduced, which I’m not particularly fond of; but I must say that in this case it produces quite elegant and readable code.

As a bonus, LambaJ also offers its own flavor of closures…

lambdaj – Project Hosting on Google Code