public static ComponentUI createSharedUI( Object key, Supplier<ComponentUI> newInstanceSupplier ) {
		if( !useSharedUIs )
			return newInstanceSupplier.get();

		return sharedUIinstances
			.computeIfAbsent( UIManager.getLookAndFeel(), k -> new IdentityHashMap<>() )
			.computeIfAbsent( key, k -> newInstanceSupplier.get() );
	}
Creates a shared component UI for the given key and the current Laf.
Each Laf instance has its own shared component UI instance.
<p>
This is for GUI builders that support Laf switching and
may use multiple Laf instances at the same time.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatUIUtils.java