为什么@FunctionalInterface具有RUNTIME保留？ [英] Why does @FunctionalInterface have a RUNTIME retention?

问题描述

Javadoc中的说法：

如果使用此注释类型注释类型，则生成错误消息所需的编译器为
，除非......

If a type is annotated with this annotation type, compilers are required to generate an error message unless ...

为什么不是 SOURCE 或 CLASS 足够，像对于 @Override 。

Why isn't SOURCE or CLASS enough, like for @Override.

推荐答案

@ FunctionalInterface 注释有两个目的。关于编译器及其必须生成的错误，确实足以在此方面具有 SOURCE RetentionPolicy 它只影响用 @FunctionalInterface 注释的类。

The @FunctionalInterface annotation serves two purposes. Regarding the compiler and the error it has to generate it would be indeed enough to have a SOURCE RetentionPolicy as in this regard it only affects the very class annotated with @FunctionalInterface.

然而，它有第二个目的，记录事实使用这个接口作为功能接口确实是有意的，并且以这种方式使用它的可能性不仅仅是巧合，例如可比较的不打算以这种方式使用。

However, it has a second purpose, documenting the fact that using this interface as a functional interface is indeed intended and the possibility to use it this way not just a coincidence like with, e.g. Comparable which is not intended to be used that way.

因此它用注释@Documented 并且具有最大 RetentionPolicy 以实现第二个目的。

Therefore it is annotated with @Documented and has the maximum RetentionPolicy to fulfill the second purpose.

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