Groovy 1.7 adds news methods to the standard Java classes. One of the new methods is eachPermutation()
. With this method we can loop through all permutations of a collection and run a closure for the iterations. To get all permutations for a collection we can use the permutations()
method.
def languages = ['Groovy', 'Clojure', 'Scala'] def result = [] languages.eachPermutation { result << it } assert 6 == result.size() assert ['Groovy', 'Clojure', 'Scala'] == result[0] assert ['Groovy', 'Scala', 'Clojure'] == result[1] assert [['Clojure', 'Groovy', 'Scala'], ['Clojure', 'Scala', 'Groovy']] == result.findAll { it[0] == 'Clojure' } // We can also get the complete list of permutations as Set. def list = [true, false] def permutations = list.permutations() assert 2 == permutations.size() assert [[false,true], [true,false]] as Set == permutations