Autoboxing not working?

Question

I have the following code:

static boolean nextPerm(int[] A) {
        int N = A.length;
        int k = N - 1;
        int[] S = { };
        while (k >= 0) {
            if (S.length > 0 && containsLarger(S, A[k])) {
                int v = firstLargest(S, A[k]);
                //int vIndex = Arrays.asList(S).indexOf(v);
                List<Integer> test = Arrays.asList(S); // // ERRORS HERE. Before error, S is { 2 } 
                System.out.println(test.get(0)); 
                int vIndex = test.indexOf(S);
                S[vIndex] = A[k];
                A[k] = v;
                System.arraycopy(S, 0, A, k + 1, N - k);
                return true;
            } else {
                S = addIntAscend(S, A[k]);
                k -= 1;
            }
        }
        return false;
    }

Before the error, S is an int array { 2 }. It errors when I set TEST to Arrays.asList(S):

Perms.java:44: error: incompatible types
                List<Integer> test = Arrays.asList(S);
                                                  ^
  required: List<Integer>
  found:    List<int[]>
1 error

Why is this happening? I thought primitives were autoboxed?

score 4 · Accepted Answer · answered Oct 09 '13 at 08:06

Have a look at this bug report which was closed as Not an Issue citing the below reason.

Autoboxing of entire arrays is not specified behavior, for good reason. It can be prohibitively expensive for large arrays.

Therefore, to convert your array to an list, you need to do this

List<Integer> test = new ArrayList<Integer>(S.length);
for (int i : S) {
    test.add(i);
}

score 3 · Answer 2 · answered Oct 09 '13 at 08:04

3

Primitives are autoboxed but arrays are not. It will work if you change your int[]'s to Integer[]'s

answered Oct 09 '13 at 08:04

Alowaniak

571
3
10

1

But look at this example. http://stackoverflow.com/a/6171675/2288418 He passes an int array to asList and is able to get the index of it. EDIT: Nevermind, there was an error in his example LOL. – Leon Helmsley Oct 09 '13 at 08:07

Autoboxing not working?

2 Answers2