LambdaJ, no more loops in Java ! LambdaJ library makes it easy to manipulate collections in a pseudo-functional and statically typed way. To iterate over collections and nested loops is often error prone, particularly when mixed with conditional statements, and it is difficult to read and maintain the resulting code. LambdaJ uses functional programming techniques to address these issues while preserving the advantages of static typing in Java. Through a straightforward DSL, LambdaJ reduces code complexity when writing iterations over collections by allowing you to filter, convert, group, aggregate and sort items with no need to write a single explicit loop. Starting from its second major release LambdaJ also offers the possibility to define and use closures and other constructs deriving from functional programming, in its usual DSL style. Attenders will learn: How to leverage the LambdaJ library to have better control over language constructs involving loops; How to eliminate unreadable loops in your code; How to implement an internal DSL in Java through a smart use of proxy and reflection; How to effectively use some functional programming techniques in Java

1. λ ambdaj An internal DSL to manipulate collections without loops by Mario Fusco mario@exmachina.ch No more loops with

5. That’s all you need to know to start using lambdaj It sounds easy, isn’t it? If you don’t believe me let’s see some EXAMPLEs & DEMOs

6. The Demo Data Model

20. How does lambdaj work? Car fastestCar = max( forEach(sales).getCar(), on(Car.class).getSpeed()); A proxy wraps the list of sales. The returned object is of class Sale but dynamically implements the Iterable interface too The getCar() invocation is propagated by the first proxy to all the sales. The cars returned by these invocations are again put in a list and another proxy, similar to the first one, is created to wrap this list, allowing to repeat this type of invocation once more (proxy concatenation). A proxy of the Car class is created in order to register the invocations on it. These invocations will be then reapplied to the cars of the former list

21. Performance analysis Minimum, maximum and average duration in milliseconds of 10 runs of 100,000 iterations of the former examples

24. lambdaj's closure Closures (or more properly first-class functions) can be defined through the usual lambdaj DSL style Closure println = closure (); { of (System.out).println( var (String.class)); } and then invoked by "closing" its free variable once: println. apply ("one"); or more times: println. each ("one", "two", "three");

28. Mario Fusco [email_address] Check out lambdaj at: code.google.com/p/lambdaj Thank you