在这种情况下，IllegalArgumentException使用API向用户传达了“不应该为空”的明确信息。正如其他论坛用户指出的那样，只要你使用API向用户传达正确的信息，你就可以使用NPE。

GaryF和tweak放弃了“有效Java”(我发誓)的参考，建议使用NPE。看看其他好的API是如何构造的，这是了解如何构造你的API的最好方法。

Another good example is to look at the Spring APIs. For example, org.springframework.beans.BeanUtils.instantiateClass(Constructor ctor, Object[] args) has a Assert.notNull(ctor, "Constructor must not be null") line. org.springframework.util.Assert.notNull(Object object, String message) method checks to see if the argument (object) passed in is null and if it is it throws a new IllegalArgumentException(message) which is then caught in the org.springframework.beans.BeanUtils.instantiateClass(...) method.

如果您选择抛出NPE，并且在方法中使用参数，显式检查null可能是多余的和昂贵的。我想VM已经为你做了。

Apache Commons Lang有一个NullArgumentException，它完成了这里讨论的许多事情:它扩展了IllegalArgumentException，并且它唯一的构造函数采用了参数的名称，而参数的名称本应该是非空的。

虽然我觉得抛出NullArgumentException或IllegalArgumentException之类的异常更准确地描述了异常情况，但我和同事们还是选择遵从Bloch在这个问题上的建议。

一般来说，开发人员不应该抛出NullPointerException异常。当代码试图解引用值为null的变量时，运行时将引发此异常。因此，如果你的方法想要显式禁止null，而不是恰好有一个空值引发一个NullPointerException，你应该抛出一个IllegalArgumentException。

二分法……它们不重叠吗?只有整体中不重叠的部分才能构成二分法。在我看来:

throw new IllegalArgumentException(new NullPointerException(NULL_ARGUMENT_IN_METHOD_BAD_BOY_BAD));

给杰森·科恩的论点投了一票，因为它表现得很好。让我一步一步地分解它。: -)

The NPE JavaDoc explicitly says, "other illegal uses of the null object". If it was just limited to situations where the runtime encounters a null when it shouldn't, all such cases could be defined far more succinctly. Can't help it if you assume the wrong thing, but assuming encapsulation is applied properly, you really shouldn't care or notice whether a null was dereferenced inappropriately vs. whether a method detected an inappropriate null and fired an exception off. I'd choose NPE over IAE for multiple reasons It is more specific about the nature of the illegal operation Logic that mistakenly allows nulls tends to be very different from logic that mistakenly allows illegal values. For example, if I'm validating data entered by a user, if I get value that is unacceptable, the source of that error is with the end user of the application. If I get a null, that's programmer error. Invalid values can cause things like stack overflows, out of memory errors, parsing exceptions, etc. Indeed, most errors generally present, at some point, as an invalid value in some method call. For this reason I see IAE as actually the MOST GENERAL of all exceptions under RuntimeException. Actually, other invalid arguments can result in all kinds of other exceptions. UnknownHostException, FileNotFoundException, a variety of syntax error exceptions, IndexOutOfBoundsException, authentication failures, etc., etc.

总的来说，我觉得NPE受到了很大的诋毁，因为传统上一直与未能遵循快速失效原则的代码联系在一起。再加上JDK未能用消息字符串填充NPE，这确实产生了一种强烈的负面情绪，这种情绪是没有根据的。实际上，从运行时的角度来看，NPE和IAE之间的区别仅限于名称。从这个角度来看，你的名字越精确，你给调用者的信息就越清晰。