public String toStringTop(int n) {
		ArrayList<String> keys = new ArrayList<String>();
		keys.addAll(countByType.keySet());
		Collections.sort(keys, new Comparator<String>() {

			@Override
			public int compare(String arg0, String arg1) {
				return (int) (get(arg1) - get(arg0));
			}
		});

		StringBuffer out = new StringBuffer();
		int i = 0;
		for (String type : keys) {
			out.append(type + "\t" + get(type) + "\n");
			i++;
			if (i++ >= n) break;
		}
		out.append(TOTAL_TYPE + "\t" + get(TOTAL_TYPE) + "\n");

		return out.toString();
	}