RFR: 8250802: Refactor StringConverter and its subclasses [v2]

[Andy Goryachev]

On Wed, 19 Nov 2025 00:42:03 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> modules/javafx.base/src/main/java/javafx/util/StringConverter.java line 38:
>> 
>>> 36: /// - Except for `DefaultStringConverter`, formatting `null` returns an empty string, otherwise the type's `toString` is
>>> 37: /// used if it is suitable; parsing `null` or an empty string returns `null`.
>>> 38: /// - Immutable (the same converter can be reused).
>> 
>> Is this true? 
>> I recall some formatters having a state, but I don't remember which...
>
> Some do, but that state is immutable. Converters build a formatter/parser on construction (if at all needed) and use it for the duration of their existence. There are some deprecations that we need to do regarding inspecting the internal state.

This is what `DateFormat` javadoc says:


Synchronization
Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.


As long as the `DateTimeStringConverter` is used only in the context of the FX application thread, we should be fine.  But can we guarantee that the application code does not try to call it from other threads?

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PR Review Comment: https://git.openjdk.org/jfx/pull/1880#discussion_r2542594368