Longest non repeating substring

longestnrsubstring.java

public static int longestNRSubstringLen(String input) {
        if(input==null)
            return 0;
          char[] array = input.toCharArray();
          int prev = 0;
 
        HashMap<Character, Integer> characterMap = new HashMap<Character, Integer>();
       
        for (int i = 0; i < array.length; i++) {
          if (!characterMap.containsKey(array[i])) {
            characterMap.put(array[i], i);
          } else {
            prev = Math.max(prev, characterMap.size());
            i = characterMap.get(array[i]);
            characterMap.clear();
          }
        }
        return Math.max(prev, characterMap.size());
   }





// java.util.* and java.util.streams.* have been imported for this problem.
// You don't need any other imports.

public static int longestNRSubstringLen(String input) {
        
    if (input == null || input.length()==0) {
        return 0;
    }
    
    int answer = 0;
    int maxAnswer = 0;
    
    for(int i=0; i<input.length(); ++i) {
        
        answer=1;
        for(int j=i+1; j<input.length(); ++j) {
            
            if(input.charAt(i)==input.charAt(j))  {
                
                break;
            }
            
            answer++;        
            
        }
        if(maxAnswer < answer) {
            maxAnswer = answer;
        }
    }

    return maxAnswer;

}