删除播放列表中的歌曲是怎么做到全部删除

                                            case 6:
                        System.out.println("删除播放列表中的歌曲");
                        System.out.println("请输入要删除歌曲的播放列表名称");
                        String playListName4 = sc.next();
                        PlayList playList3 = plc.searchPlayListByName(playListName4);
                        if (playList3 != null) {
                            System.out.println("请输入要删除歌曲id");
                            String strId1 = sc.next();
                            Song song1 = playList3.searchSongById(strId1);
                            if (song1 != null) {
                                playList3.deleteSong(strId1);
                            } else {
                                System.out.println("歌曲不存在");
                                break;
                            }
                        } else {
                            System.out.println("播放列表不存在");
                            break;
                        }
                        break;
                        //这个删除是用主播放列表进行的deleteSong方法删除，然后再用前面预设为null的那个普通播放列表的deleteSong方法删除吗
                        //还是使用什么方法一次删除主播放列表和其他播放列表中的歌曲