java - 使用 Stream 映射 Collection 结果

Question

我正在尝试想出一种无需调用 stream() 两次但无济于事的方法:

List<Song> songs = service.getSongs();

List<ArtistWithSongs> artistWithSongsList = songs.stream()
    .collect(Collectors
        .groupingBy(s -> s.getArtist(), Collectors.toList()))
    .entrySet()
    .stream()
    .map(as -> new ArtistWithSongs(as.getKey(), as.getValue()))
    .collect(Collectors.toList());

根据要求:

class ArtistWithSongs {
    private Artist artist;
    private List<Song> songs;

    ArtistWithSongs(Artist artist, List<Song> songs) {
        this.artist = artist;
        this.songs = songs;
    }
}   

是否有更优化的方法？

Answer 1

我认为在这种情况下使用 forEach 就足够了:

List<ArtistWithSongs> artistWithSongsList = new ArrayList<>();
service.getSongs().stream()
                  .collect(Collectors.groupingBy(s -> s.getArtist(), Collectors.toList()))
                  .entrySet()
                  .forEach((k, v) -> artistWithSongsList.add(new ArtistWithSongs(k, v)););