Groovy rocks!

I learned this pretty neat feature when working with Maps which otherwise puts you on the Java path in Groovy which Groovy coders do not like ;)

Let's say that you are building a Map from some data sets and the value of the map entry is a List of some data, basically a Collection.

Without knowing this groovy method of Map, one would be writing code like:

//Groovy, but not so Groovy Map map = [:] def keys = ['a','b'] keys.each{ key-> if (map[key]) { map[key] << 1 } else { map[key] = [1] } } println map //Groovier //initialize Map with default closure for key not found Map m = [:].withDefault{ [] } //withDefault in this case takes a closure that returns when a key is not found keys.each{ key-> m[key] << 1 } println m