在java中将不同的对象添加到列表中

Question

如果我有一个类 PlayList 一个类歌曲和一个类广告，并且我创建一个 Listplaylist（在另一个名为 Index 的类中）我如何将歌曲添加（或添加）到播放列表？它不允许我这样做。我不允许在其中使用 .add（索引）

public static void PrintPlayList() {
        int songsNumber = songs.size();
        int addsNumber = adds.size();
        for(int i=0; i<songsNumber;i++) {
            playlist.add(songs.get(i));

        } 

在里面声明列表之后

 public static List<PlayListStuff> playlist = new ArrayList<PlayListStuff>();

并在 PlayListStuff 类中添加字段歌曲和添加

public class PlayListStuff {
    private Song song;
    private Add  add;
}
public PlayListStuff(Song song) {
        super();
        this.song = song;

    }
    public PlayListStuff( Add add) {
        super();

        this.add = add;
    }

Answer 1

您只能将PlayListStuff 对象添加到播放列表中。

Song 和 Add 应该扩展 PlayListStuff。

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public class PlayListStuff {

}

public class Song extends PlayListStuff {

}

public class Add extends PlayListStuff {

}

Answer 2

public final class PlayList {

    private final List<Stuff> stuffs = new ArrayList<>();

    public void addStuff(Stuff stuff) {
        stuffs.add(stuff);
    }

    public interface Stuff {}
}

public class Song implements PlayList.Stuff {}

public class Add implements PlayList.Stuff {}

您的客户端代码可能如下所示：

PlayList playList = new PlayList();
playList.addStuff(new Song());
playList.addStuff(new Add());