使用lambda表达式的枚举重写方法(enum override methods using lambda expressions)

我有两个解决方案来构建一个构成比较器库的枚举：

public enum SongComparator { BY_TITLE(Comparator.comparing(Song::getTitle)), BY_ARTIST(Comparator.comparing(Song::getArtist)), BY_DURATION(Comparator.comparing(Song::getDuration)); private Comparator<Song> comp; private SongComparator(Comparator<Song> comp) { this.comp = comp; } public Comparator<Song> get() { return comp; } }

和...

public enum SongComparator2 implements Comparator<Song> { BY_TITLE { public int compare(Song s1, Song s2) { return s1.getTitle().compareTo(s2.getTitle()); }; }, BY_ARTIST { public int compare(Song s1, Song s2) { return s1.getArtist().compareTo(s2.getArtist()); }; }, BY_DURATION { public int compare(Song s1, Song s2) { return Integer.compare(s1.getDuration(), s2.getDuration()); }; }; }

如果我想用一个比较器代替枚举值，在第一个解决方案中，我必须说SongComparator.BY_TITLE.get（）; 而在第二个解决方案中，我只能说SongComparator2.BY_TITLE。

在这个意义上，第二个更好，但是，我不喜欢为每个枚举值编写public int compare ... etc，而想要像第一种方法那样使用Comparator.comparing。有没有办法做到这一点？

我几乎想要这样说：BY_TITLE {return Comparator.comparing（Song :: getTitle）; };

I have two solutions to an idea of having an enum that forms a library of comparators:

and...

If I want to substitute an enum value where a Comparator is expected, in the first solution I have to say SongComparator.BY_TITLE.get(); whereas in the second solution I can just say SongComparator2.BY_TITLE.

The second is better in this sense, however, I don't like having to write public int compare... etc for each enum value and wanted instead to make use of Comparator.comparing as in the first approach. Is there a way to achieve this?

I almost wanted to say something like: BY_TITLE { return Comparator.comparing(Song::getTitle); };

最满意答案

有什么问题：

public enum SongComparator implements Comparator<Song> { BY_TITLE(Comparator.comparing(Song::getTitle)), BY_ARTIST(Comparator.comparing(Song::getArtist)), BY_DURATION(Comparator.comparing(Song::getDuration)); private Comparator<Song> comp; private SongComparator(Comparator<Song> comp) { this.comp = comp; } public int compare(Song s1, Song s2) { return comp.compare(s1, s2); }; }

What's wrong with:

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