测试用例：

  {"abcabcbb",3}{"bbbbb",1}{"pwwkew",4} {"dvdf",3}

算法如下

public int lenghOfLongestSubString(String src) {    
  Map<Character, Integer> map = new HashMap<>();    
  int left=0;//子字符串的开始位置    
  int max=0;//子字符串的最大长度    
  char[] srcArray = src.toCharArray();    
    for (int i=0;i<srcArray.length;i++) {        
      int j;
      if (map.containsKey(srcArray[i])) {    
          j = map.get(srcArray[i]);     
         if (left <= j) {            
             left = j + 1;    
         }       
      }        
   map.put(srcArray[i], i);       
   max = Math.max(i - left + 1, max);   
  }  
 return max;
}