The javadoc for getDeclaredFields clearly states:

The elements in the returned array are not sorted and are not in any particular order.

That is the reason JNA requires the field order to be manually specified. Also see https://stackoverflow.com/questions/5001172/java-reflection-getting-fields-and-methods-in-declaration-order

Also, considering cutting out the crap with making every parameter final, every loop a Stream operation, every function an Optional chain, indent 2, etc. You've had your fun, now it's time to realize it's all counterproductive.