Length of longest substring, Java

Length of longest substring

//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;
/*
Input: "pwwkew"
Output: 3
*/
class Rextester
{  
    public static void main(String args[])
    {
        System.out.println("Hello, World!");
        System.out.println(lengthOfLongestSubstring(new String("paqwmncwkew")));
    }
    public static int lengthOfLongestSubstring(String s) {
        int left = 0;
        int right = 0;
        int[] arr = new int[256];
        int max = 0;
        while(right<s.length()){
            while(arr[s.charAt(right)] > 0) {
                arr[s.charAt(left)]--;
                left++;
            }
            arr[s.charAt(right)]++;
            max = Math.max(max, right-left+1);
            right++;
        }
        
        return max;
    }

public static int lengthOfLongestSubstringSlow(String s) {
        Set<Character> set = new HashSet<>();
        int count=1,longest=0;
        
        for(int i = 0;i<s.length();i++){
            set.add(s.charAt(i));
            for(int j = i+1;j<s.length();j++){
                if(set.contains(s.charAt(j)))
                    break;

set.add(s.charAt(j));
                count+=1;   
            }
            if(count>longest)
                longest = count;
            count=1;   
            set.clear();      
        }
        return longest;
        
    }
}


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