public class Solution {

public int lengthOfLongestSubstring(String s) {

```
if(s.length()==0) return 0;
int i=0,j=0;
int max_len = -1;
HashMap<Character, Integer> map = new HashMap<Character, Integer>();
while(j<s.length()) {
if(map.containsKey(s.charAt(j))) {
if(max_len < (j-i))
max_len = j-i;
map.remove(s.charAt(i));
++i;
} else {
map.put(s.charAt(j), j);
j++;
if(max_len < (j-i))
max_len = j-i;
}
}
return max_len;
}
```

}