How to create ArrayList (ArrayList<T>) from array (T[]) in Java

Question

I have an array that is initialised like:

Element[] array = {new Element(1),new Element(2),new Element(3)};

I would like to convert this array into an object of the ArrayList class.

ArrayList<Element> arraylist = ???;

I am sure I have done this before, but the solution is sitting just at the edge of my memory.

Answer 1

new ArrayList<Element>(Arrays.asList(array))

Answer 2

new ArrayList<T>(Arrays.asList(myArray));

Answer 3

You probably just need a List, not an ArrayList. In that case you can just do:

List<Element> arraylist = Arrays.asList(array);

Answer 4

The simplest answer is to do:

Element[] array = new Element[] { new Element(1),new Element(2),new Element(3) };
List<Element> list = Arrays.asList(array);

This will work fine. But some caveats:

1. The list returned from asList has fixed size. So, if you want to be able to add or remove elements from the returned list in your code, you'll need to wrap it in a new ArrayList(). Otherwise you'll get an UnsupportedOperationException.
2. The list returned from asList is backed by the original array. If you modify the original array, the list will be modified as well. This may be surprising.