RFR: 8355636: Reuse StringBuilder in printStackTrace [v7]

[Per Minborg]

On Sat, 26 Apr 2025 22:42:08 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> In the Throwable::printStackTrace method, StringBuilder is created multiple times to build String. By sharing StringBuilder to build String, object allocation and copying are reduced.
>> 
>> In the scenario without suppressed and ourCause, unused IdentityHashMap is not created.
>> 
>> Through these optimizations, the performance of `new Exception().printStackTrace()` can be improved by about 10%.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update src/java.base/share/classes/java/lang/Throwable.java
>   
>   Co-authored-by: Hendrik Schick <30866028+ky0n at users.noreply.github.com>

As pointed out by several reviewers above, the weighted overall benefit of this PR might be negative. Reviewers carefully need to weigh pros and cons in a plurality of dimensions, including, but not limited to:

 * Consensus in pre-communicated suggestions on the relevant mailing list
 * Readability
 * Complexity
 * Integrity
 * Maintainability
 * Adherent to current and future features
 * Test coverage and testability
 * Reviewer utilization (i.e., value over other potentially more important issues to review)
 * Archaeology
 * Performance
 * Resource utilization
 
You need to up-level and address questions like this before it becomes meaningful to spend reviewing resources on this and similar PRs.

Hence, I am expecting comments rather than code from you @wenshao  in this PR until we have established that the net benefit of this PR (contrary to the beliefs of many reviewers) can ever be positive.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/24864#issuecomment-2834195602