length of longest substring without repeating characters

gistfile1.java

public int lengthOfLongestSubstring(String s) {
      
        Boolean [] exist =new Boolean [256];
 
        for (int i=0; i<256;i++){
 
            exist[i]=false;
        }
 
        int i=0,j=0,n=s.length(),maxlen=0;
 
        while(j<n){
 
            if (exist[s.charAt(j)]){
 
                maxlen=Math.max(maxlen,j-i);
 
                while(s.charAt(i)!=s.charAt(j)){
 
                    exist[s.charAt(i)]=false;
 
                    i++;
                }
 
                i++;j++;
            }
            else{
 
                exist[s.charAt(j)]=true;
                j++;               
            }
            
        }
        return maxlen=Math.max(maxlen, n-i);
    }