Java 空构造函数

Question

所以我有两个类，称为歌曲和专辑，它们是:

    public class Songs {
    private String title;
    private Double duration;

    public Songs(String title, Double duration) {
        this.title = title;
        this.duration = duration;
    }

    public Songs(){}


    public String getTitle() {
        return title;
    }



    public Double getDuration() {
        return duration;
    }


    public static Songs addSong(String title, Double duration){
        return new Songs(title,duration);

    }
}



    import java.util.ArrayList;
import java.util.LinkedList;

public class Albums {
    private ArrayList<Songs> albums;
    private String name;
    private String title;

    public Albums(String name, String title) {
        this.albums = new ArrayList<>();
        this.name = name;
        this.title = title;
    }

    public boolean addSong(Songs songs){
        if(findSong(songs.getTitle())==null){
            this.albums.add(songs);
            return true;
        }else{
            System.out.println("Song alredy exist!");
            return false;
        }

    }

      private Songs findSong(String songName){
        for(int i=0;i<this.albums.size();i++){
            Songs currentSong = this.albums.get(i);
            if(currentSong.equals(songName)){
                return currentSong;
            }
        }
        return null;
    }
}

问题是主要的，也许我的逻辑不对，如果我遗漏了什么，请告诉我:

 public class Main {

    public static void main(String[] args) {
        Albums albums = new Albums("Alexandru", "Doi dsadcopii");
        Songs songs = new Songs("Patrascu",4.44);
        songs.addSong("Dorin",11.11);
        albums.addSong(songs);

        songs.addSong("Dorin",11.11);
        albums.addSong(songs);


        songs.addSong("Dorinsads",11.11);
        albums.addSong(songs);


        songs.addSong("Dorisadsan",11.11);
        albums.addSong(songs);



        System.out.println(songs.getTitle());

        albums.addSong(songs);

        albums.printSongs();
    }
}

为什么我得到相同的值？为什么 .addSong 中的那些值没有添加到列表中？这是我打印列表的代码:

    public void  printSongs() {
    for (int i = 0; i < this.albums.size(); i++) {
        System.out.println(i + 1 + "-->" + this.albums.get(i).getTitle() + "--->" + this.albums.get(i).getDuration());
    }

}

确实我遗漏了一些东西，但我不知 Prop 体在哪里，有什么想法可以解决这个问题吗？谢谢! :D问题是当我使用 .printSongs() 方法时它会打印第一个值

Answer 1

来自类(class)的歌曲:

public static Songs addSong(String title, Double duration){
    return new Songs(title,duration);
}

这只是返回一首新歌曲，而不是将其添加到内部列表中。

您可以直接将它们添加到相册中，例如

Albums albums = new Albums("Alexandru", "Doi dsadcopii");
albums.addSong(new Songs("Patrascu",4.44));
albums.addSong(new Songs("Dorin",11.11));