我把列表存到map里了，我只有在add里面输出才有，去别的方法里输出map

public void addPlayList(PlayList playList) {

Scanner sc2=new Scanner(System.in);

String s=sc2.next();

playListMap.put(s, playList);

}

public PlayList searchPlayListByName(String playListName) {

PlayList playList=null;

Set<String> playListSet=playListMap.keySet();

for(String s:playListSet) {

if(s.equals(playListName))

playList=playListMap.get(s);

break;

}