RFR: 8376423: Test javax/swing/plaf/metal/MetalUtils/bug6190373.java failed: ClassCastException: class java.lang.Character cannot be cast to class javax.swing.Painter [v3]

[Phil Race]

On Tue, 27 Jan 2026 20:49:05 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> The existing code only used that when creating the instance, not when retrieving an already created instance, so I don't see why we'd need to extend the lock to the retrieval.
>
> Indeed, the existing code use the lock only when creating the instance.
> 
> Yet there are quite a few places where `synchronized (classLock)` is used. In particular, `maybeInitialize` method.
> 
> https://github.com/openjdk/jdk/blob/eb6e74b1fa794bf16f572d5dbce157d1cae4c505/src/java.desktop/share/classes/javax/swing/UIManager.java#L1461-L1468
> 
> The logic in `maybeInitialize` will remain thread-safe, yet `SwingAccessor.isLafStateInitialized` can return a stale value of `false`. Thus, `SwingAccessor.getLAFStateAccessor().lafStateIsInitialized()` in `DefaultMetalTheme` can return `false` even after `UIManager` was initialised. I guess this problem existed in the original code, too.
> 
> To ensure thread-safe access to the `initialized` flag, the method `UIManager.isLafStateInitialized` has to access the flag inside the `synchronized (classLock)` block.

OK. I've updated it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29437#discussion_r2733831629