If you work on large-scale development projects, then you're familiar with the advantages of writing modular code. Well-structured, modular code is easier to write, debug, understand, and reuse. The problem for Java developers is that the functional programming paradigm has long been implemented only via specialized languages such as Haskell, Scheme, Erlang, and Lisp. This article, shows you how to use functional programming constructs such as closures and higher order functions to write well-structured, modular code in the Java language.