Specification for java.rmi.server.ObjID.hashCode asserts:

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public int hashCode()
Returns the hash code value for this object identifier, _the object number_.
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https://docs.oracle.com/en/java/javase/17/docs/api/java.rmi/java/rmi/server/ObjID.html#hashCode()

The changes done with JDK-8268764 replaced the original implementation with Long.hashCode usage
https://github.com/openjdk/jdk/commit/124f82377ba93359bc59118ee315ba194080fa92#diff-c0c1e054162cdec17bb083da268cd96be49a43ae42541d5be3906bd97b924925L203