Length of longest substring without repeating characters (Java)

/*Problem Statement:
Given a string s, find the length of the longest substring without repeating characters.

Example 1:
Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
*/

//Solution-

class Solution {
    public int lengthOfLongestSubstring(String s) {
        if(s.length()<=1)
            return s.length();
        int max=0;
        HashSet<Character> set= new HashSet<>();
        for(int i=0,j=0;i<s.length();){
            if(!set.contains(s.charAt(i))){
                set.add(s.charAt(i));
                 if(i-j+1>max)
                    max=i-j+1;
                i++;  
            }
            
            else{
               while(set.contains(s.charAt(i))){
                   set.remove(s.charAt(j));
                j++; 
               }
                set.add(s.charAt(i));
                i++;
            }
        
    }
        return max;
    }
}