RFR: 8308588: Unnecessary synchronized on GTKStyle#ICONS_MAP can be removed

[Alexey Ivanov]

On Thu, 29 Aug 2024 05:20:20 GMT, Tejesh R <tr at openjdk.org> wrote:

> > > One slight concern is that, does GTKStockIcon has any role to play with synchronized block?
> > 
> > 
> > Sorry, I didn't understand what do you mean.
> 
> I meant, since `ICONS_MAP` stores `GTKStockIcon` as value, I was wondering does that make any difference or need for the map to be synchronized?

In fact, `synchronized` block around `ICONS_MAP.get` had no effect.

To be correct, the value for `ICONS_MAP` had to be assigned inside a `synchronized` block too. Otherwise, it is not thread-safe.

> I also came across Immutable Maps which are inherently thread safe. If ICONS_MAP are immutable one, then Synchronized block is definitely redundant.

Effectively, `ICONS_MAP` is an immutable map. It's initialised in a static initialiser and is never modified afterwards.

As far as I can tell, `GTKStockIcon` objects stored in the map aren't modified either.

Thus, the entire structure is immutable and is thread-safe without additional synchronisation.

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PR Comment: https://git.openjdk.org/jdk/pull/20741#issuecomment-2317545926