LeetCode Missing Number

 1 public class Solution {
 2     public int missingNumber(int[] nums) {
 3         /*
 4         //Method 1
 5         if(nums == null || nums.length == 0){
 6             return 0;
 7         }
 8         int n = nums.length;
 9         int sum = 0;
10         for(int i = 0; i<nums.length; i++){
11             sum+=nums[i];
12         }
13         return n*(n+1)/2 - sum;
14         */
15         //Method 2
16         if(nums == null || nums.length == 0){
17             return 0;
18         }
19         int res = 0;
20         for(int i = 0; i<nums.length; i++){
21             res ^= (i+1)^nums[i];
22         }
23         return res;
24     }
25 }