In java:

        int frequency = 100;
        List<Integer> alternativeSortingList = new ArrayList<>(Collections.nCopies(100,0));
        for (Integer integer : arr) {
            alternativeSortingList.set(integer, alternativeSortingList.get(integer)+1 );
        }
        return alternativeSortingList;

Remember that the dimension of the output is predetermined... "int[100]: a frequency array"

Java 8

public static List<Integer> countingSort(List<Integer> arr) {
// Write your code here

    // Integer maxInt = Collections.max(arr);

    int[] intArr = new int[100];

    for (Integer arg : arr) {
        intArr[arg] = intArr[arg] += 1;
    }

    return Arrays.stream(intArr).boxed().collect(Collectors.toList());
}

** The Collections.nCopies(100, 0) creates a list with 100 elements, all initialized to 0 **

List count = new ArrayList<>(Collections.nCopies(100, 0)); for (int num : arr) { count.set(num, count.get(num) + 1); } return count; }

' def countingSort(arr): # Write your code here count = [0] * 100

for i in range(len(arr)):
    count[arr[i]] += 1
return count

'