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.

Answer 1

But the codenarc report it is warning like following.

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

IMO, this is bad advice on Codenarc's part as it assumes that the implementation type of [] is ArrayList. This is true today, but may not always be.

The simplest/best/usual way to create a List implementation is:

def list = []

If possible, I will usually write something like

List list = []

Just to make it a bit more obvious what this list should contain, i.e. for the sake of code readability. If I wanted to create a specific type of list I would instantiate a List "the Java way"

List list = new SomeCustomListImplementation()

But in practice I can't remember ever doing this.