what are the different ways to create an Arraylist and Hashmap in groovy

Question

I have created an ArrayList like the following:

def list = new ArrayList()

But the codenarc report it is warning like following.

ArrayList objects are better instantiated using the form "[] as ArrayList"

What are the better ways to instantiate the collections?

Answer 1

You can do:

def list = []               // Default is ArrayList
def list = [] as ArrayList
ArrayList list = []

And again, for HashMap:

HashMap map = [:]
def map = [:] as HashMap

The default in this case is a LinkedHashMap:

def map = [:] 

Answer 2

Typical is:

def list = []

other options include

def list = new ArrayList()
def list = new ArrayList<Foo>()
List list = new ArrayList()
def list = [] as ArrayList
List list = [] as ArrayList

and of course:

List<Foo> list = new ArrayList<Foo>();

Similar options exist for HashMap using [:].