在Java 8中使用Java 7 Comparators [英] Using Java 7 Comparators in Java 8

问题描述

情况

我有一个OSGi项目，我正在尝试迁移到Java 8.在我的项目中，我有依赖项我OSGi-fied的第三方库（通过添加 MANIFEST.MF 文件并将元数据放入其中）。这些库是从只读SVN存储库中检出的，因此我可以在需要时检查更新，因此我不想进行任何其他更改，而不是 MANIFEST.MF 文件，因为我无法提交它们。

I have an OSGi project that I'm trying to migrate to Java 8. In my project, I have dependencies to third party libraries that I "OSGi-fied" (by just adding the MANIFEST.MF file and putting metadata into it). These libraries are checked out from read-only SVN repositories, so I just can checkout updates from then when needed and therefore I don't want to make any other changes than in the MANIFEST.MF file, since I cannot commit them.

问题

但是，这些库使用了许多匿名比较器，如：

However, these libraries use lots of anonymous Comparators like:

private static final Comparator heightComparator = new Comparator() {
    public int compare (Object o1, Object o2) {
        return ((Glyph)o1).getHeight() - ((Glyph)o2).getHeight();
    }
};

现在，显然 java.util.Comparator interface有一大堆需要实现的新方法（当然，这会导致编译错误）。但我真的想避免实现它们或切换到Lambda表达式，因为每次检查更新版本时修改原始源很可能会导致冲突。

Now, apparently the java.util.Comparator interface has a whole bunch of new methods that need to be implemented (which, of course, leads to compilation errors). But i really want to avoid implementing them or switch to Lambda expressions because modifying the original source would most likely result in conflicts each time I check out newer revisions.

Java用于努力实现向后兼容性，我想知道为什么这么简单且广泛使用的API部分需要（相对）大量迁移。我错过了什么或是否真的不可避免？

Java used to work hard on backwards compatibility and I wonder why such a simple and widely used part of the API needs so (relatively) much effort to migrate. Am I missing something or is it really unavoidable?

推荐答案

Java 8版本中的新方法比较器是默认方法（Java 8中的一项新功能），它不仅包括方法签名，还包括默认实现。因此，较旧的 Comparator 实现应该可以在Java 8上正常工作，如果它们之前有效。

The new methods in the Java 8 version of Comparator are default methods (a new feature in Java 8) which not only include the method signature, but also a default implementation. Thus, older Comparator implementations should work just fine on Java 8 if they worked before.

如果某些东西不起作用，请告诉我们您的尝试以及错误消息。

If something is not working, please let us know what you are trying and what the error message is.

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