In this chapter, we covered closures in some depth. We covered all of the important aspects of working with closures. We explored the various ways to call a closure and the means of passing parameters. We saw how we can pass closures as parameters to methods, and how this construct can allow us to appear to add mini DSL syntax to our code.

Closures are the real "power" feature of Groovy, and they form the basis of most of the DSLs that we will develop later in this book. In the next chapter, we will build on this knowledge of closures and take a look at some more of the power features of the Groovy language, including builders and metaprogramming with the ExpandoMetaClass classes.