LeetCode-Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

 1 public class Solution {
 2    public static int lengthOfLongestSubstring(String s) {
 3         if(s == null || s.length()==0){
 4             return 0;
 5         }
 6         
 7         int len = s.length();    
 8         int l = 0;
 9         int r = 1;
10         int maxLength = 1;
11        
12         
13         HashSet<Character> set = new HashSet<Character>();
14         set.add(s.charAt(l));
15         
16         while(r < len){
17             if(!set.contains(s.charAt(r))){
18                 set.add(s.charAt(r));
19                 r ++;         
20                 maxLength = Math.max(maxLength, r-l);
21                 
22                 if(r == len){
23                     return maxLength;
24                 }
25                 
26             }
27             else{
28                 while(s.charAt(l) != s.charAt(r)){
29                     set.remove(s.charAt(l));
30                     l ++;
31                 }
32                 l ++;
33                 r ++;   
34                 if(r == len){
35                     return maxLength;
36                 }
37             }
38             
39         }
40         
41         return maxLength;
42     }
43 }