public static void IDF()
    {
        for(int i =0;i<1714;i++)
        {
            Hashtable<String, Integer> WFQ_temp= new Hashtable<String, Integer>();
         
            
            for(String word:preprocessed_list[i][1])
            {
             if(WFQ_temp.get(word)==null)
             {
                 WFQ_temp.put(word, 1);
                 if(WFQ.get(word)==null)
                 {
                    WFQ.put(word, (float)1);
                 }
                 else
                 {
                     WFQ.put(word, WFQ.get(word)+1);
                 }
             }
            }
        }
        Iterator it = WFQ.entrySet().iterator();
         while (it.hasNext()) {
                 Map.Entry pairs = (Map.Entry)it.next();
                 String Key=(String)pairs.getKey();
                 float Value=(float)pairs.getValue();
                 
                 WFQ.put(Key, (float)Math.log10((double)1714/Value));
               
         }
    }