backed List not returning a proprer size

[A. Aka]

Hi,

when I run this :

 int[] x = {1, 4, 2, 7};
        List list = Arrays.asList(x);
        System.out.println(list.size());

I have 1, instead of 4
is that normal ? I am using java8

Thanks,

[Knute Snortum]

Yes.  You have a list with one element that is an array.  Maybe you wanted to do this?

List<Integer> list = Arrays.asList(1, 4, 2, 7);

[A. Aka]

I was hoping to see autoboxing playing some role here ...

[Knute Snortum]

In what way?

[A. Aka]

1, 4, 2, 7 will be seen as Integer instead of int

[Knute Snortum]

But, they are.

List<Integer> list = Arrays.asList(1, 4, 2, 7);

The ints 1, 4, 2, 7 are autoboxed to Integers in the List.

[Tim Cooke]

The scenario the OP is seeing here is due to the signature of Arrays.asList:

static <T> List<T> asList(T... a)

When the OP does this:

int[] x = {1,2,3,4};
List list = Arrays.asList(x);

Then T becomes int[]. Meaning you have a List with a single int[] in it, hence you observe list.size() returning 1.

Make sense?