public static void main(String[] args) {

/* Test array of integers */

assert (mode(new int[] {})) == null;

assert Arrays.equals(mode(new int[] {5}), new int[] {5});

assert Arrays.equals(mode(new int[] {1, 2, 3, 4, 5}), new int[] {1, 2, 3, 4, 5});

assert Arrays.equals(mode(new int[] {7, 9, 9, 4, 5, 6, 7, 7, 8}), new int[] {7});

assert Arrays.equals(mode(new int[] {7, 9, 9, 4, 5, 6, 7, 7, 9}), new int[] {7, 9});

}

/*

public static int[] mode(int[] numbers) {

if (numbers.length == 0) return null;

HashMap<Integer, Integer> count = new HashMap<>();

for (int num : numbers) {

if (count.containsKey(num)) {

count.put(num, count.get(num) + 1);

} else {

count.put(num, 1);

}

}

int max = Collections.max(count.values());

ArrayList<Integer> modes = new ArrayList<>();

for (int num : count.keySet()) {

if (count.get(num) == max) {

modes.add(num);

}

}

return modes.stream().mapToInt(n -> n).toArray();

}