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Start your free trialShawn De
44 PointsNot understood this part
public Map<String , List<Song>> byArtist(){
Map<String , List<Song>> byArtist.get(song.getArtist());
for(Song song : mSongs ){
List<Song> artistSongs = byArtist.get(song.getArtist());
if(artistSongs == null){
artistSongs = new ArrayList<>();
byArtist.put(song.getArtist(), artistSongs);
}
artistSongs.add(song);
} return byArtist;
}
in this what will be output when artistSong == null
,
Will it print all the songs
and byArtist.put(song.getArtist(), artistSongs);
what will this code do
Darth R3id4k
Courses Plus Student 10,125 PointsDarth R3id4k
Courses Plus Student 10,125 PointsO.K. --> use JShell - it can really help you understand this. On the beginning List<Song> artistSongs is null (you didn't use "new" to point it to the object so its only null reference to nothing). Moreover
byArtist.get(song.getArtist());
returns empty (null) value for key (Artist) so the next step is to create artistSongs list for this Artist. Then
byArtist.put(song.getArtist(), artistSongs);
in map byArtist is been placed name of current artist from current song as a key and just created empty artistSongs list as a value.
If name of Artist repeat in next loop "if" condition statement will be ignored because artistSong of current artist will have value already and not returns null. Only if this statement will be given brand new Artist this variable will get null again.
I have written more here: >>>> https://teamtreehouse.com/community/regarding-the-difficulty-of-this-video