1 public int lengthOfLongestSubstring(String s) {
 2     char[] chars = s.toCharArray();

 3     //存储已遍历的元素中相应char值最后出现的位置
 4     HashMap<Character, Integer> map = new HashMap<Character, Integer>();

 5     //当遍历到i位置时，lastNoRepeatIndex到i是已遍历元素中没有重复元素出现的部分
 6     //如：abcdeefghij，当遍历到g元素，lastNoRepeatIndex=5；即第二个e的位置
 7     int lastNoRepeatIndex = 0;

 8     //最长子串的前后位置下标
 9     int[] longestIndex = {0, 0};

10     //最长子串长度
11     int longestLength = 0;
12     
13     int len = 0;
14     
15     for(int i = 0; i < chars.length; i ++) {
16         //abcdeefghiijk,遍历到i=10时，将lastNoRepeatIndex从5更新到10
17         if(map.containsKey(chars[i]) && map.get(chars[i]) + 1 > lastNoRepeatIndex) {
18             lastNoRepeatIndex = map.get(chars[i]) + 1;
19         } 
20         map.put(chars[i], i);
21         len = i - lastNoRepeatIndex +1;
22         if(len > longestLength) {
23             longestLength = len;
24             longestIndex[0] = lastNoRepeatIndex + 1;
25             longestIndex[1] = i;
26         }
27     }
28     return longestLength;
29 }