Sources are a good place to look.

Yup, no structural modifications allowed, although you can use set. It
only requires a single, tiny little object with a single reference (plus
header) to be allocated, much like an iterator. In this day and age the
cost of allocating a small object is more or less negligible. For
comparison, javac's code for concatenating two strings creates at least
four objects (it could use String.concat instead).

The clue (without looking at the docs or source) that it is a live
wrapper rather than a copy, is that the method name is asList, not toList.

Tom Hawtin

I was curious what this minimalist class was called. Now I am more
puzzled than ever:

Here is the code for Arrays.asList

   public static <T> List<T> asList(T... a) {
       return new ArrayList<T>(a);

Which indicates you actually get a full blown ArrayList. But the odd
thing is I could find no ArrayList constructor to match. There is a
collection constructor but not an array constructor. Is there some
sort of boxing happening? Am  I just not seeing the constructor for
some reason?  I don't see it in the JavaDoc either.