Groovy Nuances - Map in Groovy

Map is a data structure that takes a set of key,value pairs. Remember, Map is NOT a Collection. It is not a member of Java Collection family. It is a data structure of its own.

Groovy Map offers a few flexible ways to manipulate the contents. Totally there are 6 ways to add an element (Key,Value pair) to Map, as follows.

Let us define a Map (empty map) as follows.

def myMap = [:]

To add an element (key,value pair) we can do any of the following.

myMap[Name] = 'Raghavan'

The above Array like Syntax allows you to access a key within the square brackets and lets you specify the value after the equals sign.


We can use the get(key) method to get a value of a particular key.

println myMap.get(Age) //prints null

The Map does not have a key called Age and hence it prints null, which is no different from the Traditional Java way.


The nuance comes in the 6th step, where we use the get(key) method with a default value.

println myMap.get('Department', 'Projects')

The above statement attempts to print the value associated with the key Department in the Map myMap if exists, else it automatically adds a key, value (Deparment=Projects) into the Map.

println myMap
println myMap.get('Department')` //subsequent attempt will not throw any nulls, as it was recently inserted

Raghavan alias Saravanan Muthu
16 Jan 2021 | Tue | 07 46 PM IST