leetcode--Longest Substring Without Repeating Characters

 1 public class Solution {
 2     public int lengthOfLongestSubstring(String s) {
 3         int len = 0;
 4         HashSet<Character> hset = new HashSet<Character>(); 
 5         if(s.length() > 0){
 6             StringBuffer temp = new StringBuffer();
 7             temp.append(s.charAt(0));
 8             hset.add(s.charAt(0));
 9             ++len;
10             for(int i = 1; i < s.length(); ++i){
11                 if(hset.contains(s.charAt(i))){
12                     StringBuffer abf = new StringBuffer();
13                     abf.append(s.charAt(i));                    
14                     int index = temp.indexOf(abf.toString());
15                     temp.delete(0, index + 1);
16                 }
17                 else
18                     hset.add(s.charAt(i));                
19                 temp.append(s.charAt(i));
20                 if(temp.length() > len)
21                     len = temp.length();
22             }            
23         }
24         return len;
25     }
26 }