Easy 389题 Find the Difference

Question：Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.
Find the letter that was added in t.
public class Solution {
public char findTheDifference(String s, String t) {
// char result=s.charAt(0); //there is a possibility that s is null and t has only one element
int i;
String str=s+t;
char result=str.charAt(0);
for(i=1;i<=str.length()-1;i++)
{
result^=str.charAt(i);
}
return result;
}
}

It's almost same as "single number". We use ^ again
exclusive OR operation（异或）。。。