java - 将代码设计为以不同方式处理空集合和 null 值是好事还是坏事？

Question

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Answer 1

在他的(非常好的)书 Effective Java 中，Joshua Bloch 针对方法的返回值处理了这个问题(不像您的问题那样“一般”):

(About use of null) It is errorprone, because the programmer writing the client might forget to write the special case code to handle a null return.

(...)

It is sometimes argued that a null return value is preferable to an empty array because it avoids the expense of allocating the array. This argument fails on two counts. First, it is inadvisable to worry about performance at this level unless profiling has shown that the method in question is a real contributor to performance problems (Item 55). Second, it is possible to return the same zero-length array from every invocation that returns no items because zero-length arrays are immutable and immutable objects may be shared freely (Item 15).

(...)

In summary, there is no reason ever to return null from an array- or collection-valued method instead of returning an empty array or collection. (...)

就我个人而言，在我的代码中使用集合时，我将此推理作为经验法则。当然，在某些情况下 null 和 empty 之间的区别是有意义的，但根据我的经验，这种情况很少见。

尽管如此，正如 BionicCode 在评论部分所述，如果方法返回 null 而不是 empty 以指定出了点问题，您总是有可能抛出异常.