Valid Anagram

Given two strings s and t, write a function to determine if t is an anagram of s.
For example,
s = "anagram", t = "nagaram", return true.
s = "rat", t = "car", return false.
Note:
You may assume the string contains only lowercase alphabets.
Follow up:
What if the inputs contain unicode characters? How would you adapt your solution to such case?
Solution:
1. public class Solution {
2. public boolean isAnagram(String s, String t) {
3. if (s == null || t == null || s.length() != t.length())
4. return false;
5. 6. int[] arr = new int[128];
7. 8. for (int i = 0; i < s.length(); i++) {
9. arr[(int)s.charAt(i)]++;
10. arr[(int)t.charAt(i)]--;
11. }
12. 13. for (int i = 0; i < arr.length; i++) {
14. if (arr[i] != 0)
15. return false;
16. }
17. 18. return true;
19. }
20. }