public static List<String> getDiffrent4(List<String> list1, List<String> list2) 
    {           
           Map<String,Integer> map = new HashMap<String,Integer>(list1.size()+list2.size());
           List<String> diff = new ArrayList<String>();
           List<String> maxList = list1;
           List<String> minList = list2;
           if(list2.size()>list1.size())
           {
               maxList = list2;
               minList = list1;
           }
           
           for (String string : maxList) 
           {
              map.put(string, 1);                    
           }
           
           for (String string : minList) 
           {
               Integer cc = map.get(string);                    
               if(cc!=null)                    
               {
                   map.put(string, ++cc);
                   continue;                    
               }           
               map.put(string, 1);                    
           }
           
           for(Map.Entry<String, Integer> entry:map.entrySet())                    
           {                    
               if(entry.getValue()==1)                    
               {                    
                   diff.add(entry.getKey());                    
               }                    
           }                               
           return diff;                    
    }