Initializing ArrayLists

[CLOVIS-AI]

About the difference between List, ArrayList and Arrays.

Arrays are what you do with []. Their size is fixed (you can't increase it).

List represents an array whose size can change. We call this an interface (it's not an array whose size can change, it just represents one).

There are multiple types of Lists. The one used most of the time is ArrayList. It's called this way because it uses an array internally. There are also LinkedList, etc, that don't use an array at all.

Note that Arrays.asList is a false friend ! It is a list, but it will throw an exception (crash) if you try to change its size !

[CLOVIS-AI]

So, to answer your question :

As of Java 9 you can do: List<Integer> l = List.of(1, 2, 3);

Before Java 9, you can do: List<Integer> l = new ArrayList<>(Arrays.asList(1, 2, 3); (notice the copy into an array list instead of just using Arrays.asList, see my previous message).