Spread operator

Spread operator helps Groovy collections (list, range and map) to simple comma separated values. Spread operator is so flexible which can be used anywhere. For example:

def test(a, b, c){

return a + b + c

}

def numList = [1, 2, 3]

If you want to pass the above list of values to the test() method you have to write some boilerplate code to extract the elements and pass them in the method.

Whereas the spread operator is introduced to eliminate boilerplate code and follow clean coding. The above method can be called with the given list without a single extra line of code.

test(*numList)

An asterisk followed by list, range or map will spread the collection and convert all the containing values to comma separated values. The above example will work same for Range.

def numRange = 1..3

test(*numRange)

Map has different syntax compared to List and Range.

def aMap = [a:1, b:2]

def bMap = [c:3, *:aMap]

Likewise Groovy contains many such shortening facilities where development time can be reduces and code can remain clear and understandable.