LeetCode 136 Single Number

Given an array of integers, every element appears twice except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

public int singleNumber(int[] nums) {
int k = 0;
for (int i = 0; i <nums.length ; i++) {
k = k^nums[i];
}
return k;
}