1497. Check If Array Pairs Are Divisible by k 

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class Solution {
    public boolean canArrange(int[] arr, int k) {
        Map<Integer, Integer> numToFrequencyMap = new HashMap<>();

        for (int num : arr) {
            num = (num % k + k) % k;
            numToFrequencyMap.put(num, numToFrequencyMap.getOrDefault(num, 0) + 1);
        }

        for (Map.Entry<Integer, Integer> entry : numToFrequencyMap.entrySet()) {
            int num = entry.getKey();
            int frequency = entry.getValue();
            if (num > 0 && numToFrequencyMap.getOrDefault(k - num, 0) != frequency) {
                return false;
            }
        }

        return numToFrequencyMap.getOrDefault(0, 0) % 2 == 0;
    }
}

References

1497. Check If Array Pairs Are Divisible by k