`java.lang.ref.Reference.enqueue` method clears the reference object before it is added to the registered queue. When the `enqueue` method is called, the reference object is cleared and `get()` method will return null in JDK 9.

Typically when a reference object is enqueued, it is expected that the reference object is cleared explicitly via the `clear` method to avoid memory leak because its referent is no longer referenced. In other words the `get` method is expected not to be called in common cases once the `enqueue`method is called. In the case when the `get` method from an enqueued reference object and existing code attempts to access members of the referent, `NullPointerException` may be thrown. Such code will need to be updated.