Length of Last Word

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.
If the last word does not exist, return 0.
Note: A word is defined as a character sequence consists of non-space characters only.
For example,
Given s = "Hello World",
return 5.
Solution:
1. public class Solution {
2. public int lengthOfLastWord(String s) {
3. if (s == null)
4. return 0;
5. 6. int i = s.length() - 1;
7. 8. while (i >= 0 && s.charAt(i) == ' ') { i--; }
9. 10. int j = i;
11. 12. while (i >= 0 && s.charAt(i) != ' ') { i--; }
13. 14. return j - i;
15. }
16. }