1207_Unique_Number_of_Occurrences.java

class Solution {
    public boolean uniqueOccurrences(int[] arr) {
       Map<Integer, Integer> map = new HashMap();
        for(int num : arr) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        Set<Integer> set = new HashSet(map.values());
        return map.size() == set.size();
    }
}