After I read the chapter 6 "closures" of the book Groovy and Grails Recipe, and I decided to use the power of closures of Groovy for resource (files) with other problem that I had, decompile in one step every class of jar library. Well, the purpose of this class is call an external java decompiler (jad) from a Groovy class and execute the command into directory where the jar file was decompressed. And by using the power of closures executes recursively into this directory until find the classes. Well, no more words, here the class package demo class Executor { // directory where the library(jar) was decompressed def path /** * Execute the decompilation of the classes into the directory defined in the path * @return */ def decompileClasses(){ def directory = new File(path) //make use of closures defined in the Object class directory.eachFileRecurse { def name = it.absolutePath //if the current resource hasn't a .class extension continues with