How to convert an ArrayList containing Integers to primitive int array?

Question

I\'m trying to convert an ArrayList containing Integer objects to primitive int[] with the following piece of code, but it is throwing compile time error. Is it possible to

Answer 1

Arrays.setAll()

    List x = new ArrayList<>(Arrays.asList(7, 9, 13));
    int[] n = new int[x.size()];
    Arrays.setAll(n, x::get);

    System.out.println("Array of primitive ints: " + Arrays.toString(n));

Output:

Array of primitive ints: [7, 9, 13]

The same works for an array of long or double, but not for arrays of boolean, char, byte, short or float. If you’ve got a really huge list, there’s even a parallelSetAll method that you may use instead.

To me this is good and elgant enough that I wouldn’t want to get an external library nor use streams for it.

Documentation link: Arrays.setAll(int[], IntUnaryOperator)