void testEachStyleTopN() {
		int nTop = 10;
		Map<String, List<Song>> res = topService.eachStyleTopN(nTop);
		if(res == null) {
			System.err.println("NO RESULT FOUND...");
			return ;
		}
//		Set<Entry<String,List<Song>>> iter = res.entrySet();
		for ( Entry<String, List<Song>> e : res.entrySet() ) {
			System.err.println( e.getKey() + " TOP " + nTop + ":");
			List<Song> top = e.getValue();
			if (top == null) System.err.println("NO VALUE FOR KEY...");
			else {
				int i = 0;
				for( Song s : top ) {
					System.err.print(++i + " " + s.getPlaycount() + " ");
					System.err.println(s);
				}
			}
		}
	}