On Thu, 21 Aug 2025 02:00:47 GMT, Guanqiang Han <[email protected]> wrote:
>> src/java.base/share/classes/java/lang/Class.java line 4160:
>>
>>> 4158: // Checks whether the class name exceeds the maximum allowed
>>> length.
>>> 4159: private static boolean classNameLengthIsValid(String name) {
>>> 4160: Objects.requireNonNull(name);
>>
>> This is not needed as the `name.length()` call already performs an implicit
>> `null` check.
>
> hi @ExE-Boss ,thanks for your comment regarding the
> Objects.requireNonNull(name) call. I understand that name.length() triggers
> an implicit null check, which could make the explicit check seem redundant.
>
> However, I wonder if there is a subtle difference worth considering here: the
> implicit null check relies on the system exception (signal) mechanism and
> subsequent JVM handling, which does have some overhead. In addition, as i
> know, C2 decides whether to use implicit null checks after performing
> statistical analysis. For this kind of core library, should we assume that
> null is a low-probability event?
Well, **C2** can elide even explicit `null` checks, but
`Objects.requireNonNull(name)` doesn’t ([currently][JDK‑8233268][^1]) get a
helpful message like what an implicit null check gets.
[JDK‑8233268]: https://bugs.openjdk.org/browse/JDK-8233268
[^1]: https://git.openjdk.org/jdk/pull/26600
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PR Review Comment: https://git.openjdk.org/jdk/pull/26802#discussion_r2296091939
