JDK-8352891 Performance improvements to ByteArrayOutputStream

[Alan Bateman]

On 31/03/2025 16:51, Engebretson, John wrote:
>
>   Alan – is this what you have in mind:
>
> ByteArrayOutputStream.getInstance() // returns existing class
>
> ByteArrayOutputStream.getUnsynchronizedInstance() // returns subclass 
> of BAOS that overrides the synchronization
>
> ByteArrayOutputStream.get<Scalable|Memory|Fast|Segmented>Instance() // 
> returns the new class
>
>

BAOS has been synchronized since JDK 1.0. While undocumented, it's 
possible that existing code depends on this 30 year behavior so I think 
we are stuck with it.

The removal of biased locking has spurred on a few complaints that the 
class is needlessly synchronized. A static factory to return an 
unsynchronized BOAS would help but only if it isn't used with code that 
assumes all operations are synchronized. So I think we will have to look 
at the API docs for this.

It's not clear that we need to have several implementation with 
different performance tradeoffs. So I think part of the exploration will 
be to see what usages perform better or worse, and whether having a 
parameter to specify the initial size or some hint of the max size would 
help the discussion.

-Alan

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/core-libs-dev/attachments/20250402/7a0f0e1f/attachment-0001.htm>