Find the longest substring without repeating characters

Sliding Window is a subarray running on a large array, which is a collection of underlying elements. Here we use two pointers, one pointer A always selects the first char of the max substring, from each iteration of the string. The second pointer B runs ahead of pointer A, until a duplicate character is found or the end of the string is reached. 


public int lengthOfLongestSubstring(String s) {

        int a_pointer = 0;
        int b_pointer = 0;
        int max = 0;
        
        Set<Character> hashSet = new HashSet<>();
        int i = 0;
        
        while(b_pointer < s.length()) {

            if(!hashSet.contains(s.charAt(b_pointer))) {
              hashSet.add(s.charAt(b_pointer));
              b_pointer++;
              max = Math.max(hashSet.size(), max);
            } else {
              hashSet.remove(s.charAt(a_pointer));
              a_pointer++;
            }
        }

        return max;
    }

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