Java solution in "2 lines"
\nclass Solution {\n    public List<Integer> findLonely(int[] nums) {\n        var freqMap = Arrays.stream(nums).boxed()\n            .collect(Collectors.groupi
```\nclass Solution {\n    public List<Integer> findLonely(int[] nums) {\n        var freqMap = Arrays.stream(nums).boxed()\n            .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));\n\n        return Arrays.stream(nums).boxed().filter(e -> \n                freqMap.get(e) == 1 && !freqMap.containsKey(e+1) && !freqMap.containsKey(e-1))\n            .collect(Collectors.toList());\n    }\n}\n```
['Java']