Java Solution
Code\n\nclass Solution {\n    public int[] separateDigits(int[] nums) {\n        int amount = 0;\n        List<List<Integer>> lists = new ArrayList<>();\n      
# Code\n```\nclass Solution {\n    public int[] separateDigits(int[] nums) {\n        int amount = 0;\n        List<List<Integer>> lists = new ArrayList<>();\n        for (int n : nums) {\n            List<Integer> list = new ArrayList<>();\n            while (n > 0) {\n                list.add(n % 10);\n                n /= 10;\n            }\n            amount += list.size();\n            lists.add(list);\n        }\n        int[] arr = new int[amount];\n        int count = 0;\n        for (List<Integer> list : lists) {\n            for (int i = list.size() - 1; i >= 0; i--) {\n                arr[count++] = list.get(i);\n            }\n        }\n        return arr;\n    }\n}\n```
['Java']