Missing Ranges

Given a sorted integer array where the range of elements are in the inclusive range [lower, upper], return its missing ranges.

Example

Example 1

Input:
nums = [0, 1, 3, 50, 75], lower = 0 and upper = 99
Output:
["2", "4->49", "51->74", "76->99"]
Explanation:
in range[0,99],the missing range includes:range[2,2],range[4,49],range[51,74] and range[76,99]

Example 2

Input:
nums = [0, 1, 2, 3, 7], lower = 0 and upper = 7
Output:
["4->6"]
Explanation:
in range[0,7],the missing range include range[4,6]

public class Solution {
    public List<String> findMissingRanges(int[] nums, int lower, int upper) {
        List<String> ans = new ArrayList<>();
        for (int i = 0; i < nums.length; i++) {
            // Handling outer limits
            if (i == 0) {
                long l = lower;
                l--;
                String interval = interval(l, (long) nums[i]);
                if (interval.length() != 0)
                    ans.add(interval);
            }
            if (i == nums.length - 1) {
                long u = upper;
                u++;
                String interval = interval((long) nums[i], u);
                if (interval.length() != 0)
                    ans.add(interval);
            }
            // Handling array intervals
            if (i != nums.length - 1) {
                String interval = interval((long) nums[i], (long) nums[i + 1]);
                if (interval.length() != 0)
                    ans.add(interval);
            }
        }
        if (nums.length == 0) {
            long l = lower, u = upper;
            l--;
            u++;
            String interval = interval(l, u);
            if (interval.length() != 0)
                ans.add(interval);
        }
        return ans;
    }

    public String interval(long start, long end) {
        if (end - start == 2)
            return Long.toString(start + 1);
        else if (end - start > 2) {
            String interval = Long.toString(start + 1) + "->" + Long.toString(end - 1);
            return interval;
        } else
            return "";
    }
}