Groovy for Domain-specific Languages - Second Edition

Closures and collection methods

In the last chapter, we encountered Groovy lists and saw some of the iteration functions, such as the each method:

def flintstones = ["Fred","Barney"]

flintstones.each {
    println "Hello, ${it}"
}

This looks like it could be a specialized control loop similar to a while loop. In fact, it is a call to the each method of Object. The each method takes a closure as one of its parameters, and everything between the curly braces {} defines another anonymous closure.

Closures defined in this way can look quite similar to code blocks, but they are not the same. Code defined in a regular Java or Groovy style code block is executed as soon as it is encountered. With closures, the block of code defined in the curly braces is not ...