Length of Last Word

Problem:

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:

 public class Solution {  
   public int lengthOfLastWord(String s) {  
     int pos=0;   
     for(int i=s.length()-1;i>=0;i--)  
      {  
         if(s.charAt(i)!=' ')  
          pos++;  
         else if(pos>0 && s.charAt(i)==' ')  
          break;  
      }  
      return pos;  
   }  
 }  

Discussion:

I first attempt was from the beginning of the string, but failed to consider the situation when "a ". Then I tried iterate from tail of the string then succeeded.