실패율→배열에서 동일요소를 세기 위한 방법★★★

나의 풀이 

public class Solution {
    public int[] solution(int N, int[] stages) {
        Map<Integer, Double> result = new HashMap<>();
        int length = stages.length;
        for (int idx = 1; idx <= N; idx++) {
            if (length != 0) {
                int count = 0;
                for (int stage : stages) {
                    if (stage == idx) {
                        count++;
                    }
                }
                result.put(idx, (double) count / length);
                length -= count;
            } else {
                result.put(idx, 0.0);
            }
        }
        List<Integer> sortedKeys = new ArrayList<>(result.keySet());
        Collections.sort(sortedKeys, (key1, key2) -> result.get(key2).compareTo(result.get(key1)));
        return sortedKeys.stream().mapToInt(i -> i).toArray();
    }
}

▶ result.get(key2).compareTo(result.get(key1)) → 내림차순하기 위한 코드