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Lingjian Kong
6,330 PointsartistSongs.add(song)
Hi,
In
private Map<String, List<Song>> byArtist() {
Map<String, List<Song>> byArtist = new HashMap<>();
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;
}
We have artistSongs.add(song);
When we are not creating a new song list for a new artist, it seems to me that it only adds the song to the local List "artistSongs", without putting it into the map by "byArtist.put(song.getArtist(), artistSongs);" Why don't we add byArtist.put(song.getArtist(), artistSongs); after artistSongs.add(song);?
Could someone clarify it for me?
1 Answer
Vidhya Sagar
1,568 PointsYes you can. It is perfectly legal to do that. Since it is a List<Song> type and it is a list it will get updated instantaneoulsy at runtime. But when you do that if the Map has not been created then it will come inside the if and add the song and since there is no else statement it will continue and add the song again , because there is an add option again outside the if condition . One way is by using else. IF you use else , then what you are suggesting will work. or the song will get added twice(one for add inside the if and again one for the add outside the if) whenever a new Map is created. Hope this helps.