public static int lengthOfLongestSubstring2(String s) {
int len = 0, left = 0, index = 0;
char[] chars = s.toCharArray();
for (int i = 0; i < chars.length; i++) {
for (int j = left; j < i; j++) {
if (chars[j] == chars[i]) {
left = j + 1;
break;
}
}
if (i - left + 1 > len) {
len = i - left + 1;
index = left;
}
}
System.out.println(s.substring(index,index+len));
return len;
}