为什么checkNotNull（）没有用@Nonnull注释 [英] Why checkNotNull() is not annotated with @Nonnull

问题描述

我发现 checkNotNull（） guava中的前提条件不方便 @Nonull 注释。请考虑以下示例：

I found inconvenient that checkNotNull() precondition in guava is not marked with @Nonull annotation. Consider following example:

State(Set<Model> models, Set<Variation> variations) {
  this.models = checkNotNull(models);
  this.variations = checkNotNull(variations);

  if (this.variations == null) {
     throw new IllegalArgumentException();
  }
  this.engine = createEngine();
}

因此IDE无法找到 variants == null 始终为false。是否有任何特殊原因导致此前置条件未标记为 @Nonull （即使它的参数是使用 @Nullable 定义的）。

So IDE could not found that variations == null is always false. Is there any particular reasons why this precondition is not marked with @Nonull (even if it's arguments are defined using @Nullable).

推荐答案

我们还没有在任何地方使用 @Nonnull ，抱歉。为什么？我们尝试添加更多的空检查注释，我们发现：

We haven't used @Nonnull anywhere, sorry. Why? We tried adding more null-checking annotations, and we found that:

• 添加所有其他注释非常详细。


• @Nullable 是 NullPointerTester 所需的全部内容。不可否认，对Guava开发者而言，这比Guava用户更重要。


• @Nullable 似乎已经解决了大多数问题。我承认很难说在用户找到之前会有多少未经检入的错误其他注释。

• Adding all the other annotations is highly verbose.
• @Nullable is all we need for NullPointerTester. Admittedly that's more important to Guava developers than Guava users.
• @Nullable appeared to have caught most problems. I admit it's hard to say how many un-checked-in bugs other annotations would have caught before the user found them.

详细程度是主要的事情。它变得疯狂，特别是在子类型和参数化类型的情况下。我们试图为注释选择一个最佳点。也许有一天我们会改变它。但就目前而言，这就是事情的原因。

The verbosity was the main thing. It gets crazy, especially with subtyping and with parameterized types. We tried to pick a sweet spot for annotations. Maybe we'll change it one day. For the moment, though, that's why things are the way they are.

（如果我们做了某件事，我怀疑我们会尝试制作 @Nonnull 默认情况下，使用 @CheckForNull 代替例外。但是我还没有调查它甚至足以确保我已经意思是正确的。）

(If we did do something, I suspect we'd try to make @Nonnull the default, using @CheckForNull for the exceptions instead. But I haven't looked into it even enough to make sure I've got the meanings right.)

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