What is `Cleaner` API in Java 9+ and how does it improve over `finalize()`?

Explanation

Cleaner in Java 9+ improves over finalize() by providing a way to register cleanup actions after an object becomes phantom-reachable, avoiding the performance and ordering issues of finalize() without resurrecting the object.

Key points

Cleaner API registers cleanup actions for phantom-reachable objects
Avoids performance and ordering problems of finalize()
Does not resurrect the object after cleanup
Cleaner is not a replacement for garbage collection or a faster version of finalize()

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