static void indexStatistic(){
		/*record # of entries with different hitting number */
		long entryRcord[] = new long[7];
		Iterator<Entry<String, long[]>> iter = index.entrySet().iterator();
		while(iter.hasNext()){
			Entry<String, long[]> entry= iter.next();
			long meta[] = new long[M+2];
			meta = entry.getValue();
			if(meta[0]<=5){
			entryRcord[(int) meta[0]]++;	
			}else{
				entryRcord[6]++;
			}
		}
		int i=0;
		for(i=0;i<6;i++){
			resultRecord.println("# of entries with counter " +i+" : " + entryRcord[i]);
		}
			resultRecord.println("# of entries with counter larger than " +i +" : " +entryRcord[i]);
	}