RFR: 8368328: CompactNumberFormat.clone does not produce independent instances

[Justin Lu]

On Wed, 24 Sep 2025 17:37:59 GMT, Naoto Sato <naoto at openjdk.org> wrote:

> Fixing `CompactNumberFormat.clone()` to clone mutable reference objects. The bug was caused by accessing the shared objects concurrently which resulted in an illegal state on parsing. There are other reference fields that are shared, but the contents of those fields (such as prefix/suffix) are constants/read-only, so they may be shared.

src/java.base/share/classes/java/text/CompactNumberFormat.java line 2508:

> 2506:     @Override
> 2507:     public CompactNumberFormat clone() {
> 2508:         CompactNumberFormat other = (CompactNumberFormat) super.clone();

Maybe a comment indicating why we don't need to handle the `List<Patterns>` fields would be helpful for maintainers. (Since they are read-only after construction.) Otherwise we have to dig around the use sites to figure that out.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/27475#discussion_r2377131363