抛出NullPointerException。我不知道哪里出了问题。这是一种显示特定歌曲的歌手姓名的方法
公共列表queryArtistForSong(String songName,int sortOrder){
StringBuilder sb = new StringBuilder(QUERY_ARTIST_FOR_SONG_START);
sb.append(songName);
sb.append("\"");
if(sortOrder != ORDER_BY_NONE) {
sb.append(QUERY_ARTIST_FOR_SONG_SORT);
if(sortOrder == ORDER_BY_DESC) {
sb.append("DESC");
} else {
sb.append("ASC");
}
}
System.out.println("SQL Statement: " + sb.toString());
try (Statement statement = con.createStatement();
ResultSet results = statement.executeQuery(sb.toString())) {
List<SongArtist> songArtists = new ArrayList<>();
while(results.next()) {
SongArtist songArtist = new SongArtist();
songArtist.setArtistName(results.getString(1));
songArtist.setAlbumName(results.getString(2));
songArtist.setTrack(results.getInt(3));
songArtists.add(songArtist);
}
return songArtists;
} catch(SQLException e) {
System.out.println("Query failed: " + e.getMessage());
return null;
}
}