public String serializeParamsInfo() {
		String line = "";
		List<Map.Entry<String, Integer>> infoIds = new ArrayList<Map.Entry<String, Integer>>(
				params.entrySet());
		// HashMapе value 
		Collections.sort(infoIds, new Comparator<Map.Entry<String, Integer>>() {
			public int compare(Map.Entry<String, Integer> o1,
					Map.Entry<String, Integer> o2) {
				return (o2.getValue()).toString().compareTo(
						o1.getValue().toString());
			}
		});
		line+=pageFreq+"\t";
		line+=infoIds.size();
		// HashMapе value  ʾ
		for (int i = 0; i < infoIds.size(); i++) {
			String id = infoIds.get(i).toString();
			line+="\t"+id;
		}
		return line;
	}