Java 8 getter应该返回可选类型吗？ [英] Should Java 8 getters return optional type?

问题描述

Java 8中引入的可选类型对许多开发人员来说是一个新东西。

Optional type introduced in Java 8 is a new thing for many developers.

是一个getter方法返回可选< Foo> 代替经典 Foo 一个好习惯？假设值可以是 null 。

Is a getter method returning Optional<Foo> type in place of the classic Foo a good practice? Assume that the value can be null.

推荐答案

当然，人们会做他们想做的事。但是在添加此功能时我们确实有一个明确的意图，并且不是一个通用的可能类型，就像许多人希望我们这样做。我们的目的是为库方法返回类型提供一种有限的机制，其中需要一种明确的方式来表示无结果，并且使用 null 这样的绝大多数可能是导致错误。

Of course, people will do what they want. But we did have a clear intention when adding this feature, and it was not to be a general purpose Maybe type, as much as many people would have liked us to do so. Our intention was to provide a limited mechanism for library method return types where there needed to be a clear way to represent "no result", and using null for such was overwhelmingly likely to cause errors.

例如，您可能永远不应该将它用于返回结果数组或结果列表的内容;而是返回一个空数组或列表。您几乎不应该将它用作某事物或方法参数的字段。

For example, you probably should never use it for something that returns an array of results, or a list of results; instead return an empty array or list. You should almost never use it as a field of something or a method parameter.

我认为通常使用它作为getter的返回值肯定会被过度使用。

I think routinely using it as a return value for getters would definitely be over-use.

没有任何错误的可选，应该避免它，这不是很多人所希望的，因此我们非常关注热心过度使用的风险。

There's nothing wrong with Optional that it should be avoided, it's just not what many people wish it were, and accordingly we were fairly concerned about the risk of zealous over-use.

（公共服务公告：从不致电 Optional.get 除非您能证明它永远不会为null;而是使用其中一种安全方法，例如 orElse 或 ifPresent 回想起来，我们应该调用 get 类似 getOrElseThrowNoSuchElementException 之类的东西，或者更清楚地说这是一个高度的东西首先破坏了 Optional 的整个目的的危险方法。经验教训。（更新：Java 10有 Optional.orElseThrow（），它在语义上等同于 get（），但其名称更合适。））

(Public service announcement: NEVER call Optional.get unless you can prove it will never be null; instead use one of the safe methods like orElse or ifPresent. In retrospect, we should have called get something like getOrElseThrowNoSuchElementException or something that made it far clearer that this was a highly dangerous method that undermined the whole purpose of Optional in the first place. Lesson learned. (UPDATE: Java 10 has Optional.orElseThrow(), which is semantically equivalent to get(), but whose name is more appropriate.))

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